In 3000 Leagues in Search of Mother (and the story that was its basis), one of the reasons why Marco Rossi is so desperate to find his mother Anna is that her last letter implies that her health is decaying. Which means she might never come back home. When Marco finally finds her, she's so ill and so depressed that she's rejecting one last operation that could save her life, despite the pleas of her doctor and her benevolent bosses. Seeing Marco again gives Anna the strength to go through the surgery, and she's saved.
Aldnoah.Zero has Lemrina, a teenage girl who must use a wheelchair to move around and is only able to walk very short distances when in a low gravity environment. She's an illegitimate princess from Mars and, with some holographic disguises, she becomes the Body Double of her currently comatose older half-sister Asseylum, whom she resents heavily.
There were four in Angel Beats! when they were still alive: Masami Iwasawa (suffered a stroke after being hit on the head by her abusive father and died in the hospital), Yui (was quadriplegic after an accident and languished away in bed until she kicked it), Otonashi's dead little sister Hatsune (undisclosed illness that ultimately kills her) and Kanade "Angel" Tachibana (heart illness that leads her to need a transplant). In fact, after the latter died, her main goal was to find and thank the person who donated their heart to her and allowed her to live a little longer... Said person turned out to be the male lead Otonashi.
Angelic Layer: The mother of the main character, Shuuko, is an adult Ill Girl who abandoned her daughter because she "didn't want to be a burden" and feared Misaki would be ostracized for having a "useless" mother. This gives her somewhat of an excuse for literal Parental Abandonment, leaving Misaki in the "more capable" care of her aunt. (Meanwhile, the entire Angelic Layer game is an elaborate plan coming from her friend Icchan to get enough data on human neurophysiology to cure this disease.) Curiously, this is not in the manga at all.
Attack No. 1: Kozue Ayuhara is ill and has to quit sports awhile and move where she can rest because of it, until she comes back and joins the volleyball team.
Bakuten Shoot Beyblade: The third season has Monica, the younger sister of Moses. Her illness is never named but is quite serious as she needs a pricey operation badly. Moses became a blader at BEGA specifically to help pay for it.
In Binbou Shimai Monogatari Asu winds up in hospital from a neglected cold, giving her sister Kyou the chance to indulge in emotional memories about the time their mother was hospitalized.
The title character of Binetsu Shoujo ("Feverish Girl"), Rina Kisaragi. She has anemia and tends to pass out quite a bit, so she often goes to a local hospital for check-ups.
In Black Butler, Ciel's Missing Mom Rachel Durless was asthmatic and passed her illness on her son. Her sister Angelina aka the future "Madame Red" got the idea of becoming a doctor from her desire to help Rachel with her health problems.
Black Jack: The title character had five female patients in the new anime series:
Pinoko, his adopted daughter assistant. She was originally a sentient tumor in the body of a young girl, whom he extirped and gave a doll-like body out of pity since he found out that she strongly wished to live, just like Black Jack wanted to after the accident that killed his mother and left him paralyzed for years. Pinoko's sister had a Freak Out and disowned her, so Black Jack took the kid around as his adoptive daughter and assistant.
Michiru, a Teen Genius manga artist whose biggest dream was to get married before she died, so Black Jack played the charade to make her accept the operation that would save her, later "breaking up" with her so she wouldn't let her one-sided love for him stunt her. She not only gets better, but ends up marrying her Unlucky Childhood Friend.
Watou and Kumiko's classmate Rei, an Idol Singer who takes her career as reallySerious Business, but has a tumor in her throat that will put it in serious risks.
Megumi Kisaragi, a female doctor whom Black Jack fancied, but had advanced ovarian cancer. After having her affected inner organs removed, she changed her name to Kei and left, living her life as a male, despite not being outright said if she went through a sex change or not.
In the backstory, there is another: Black Jack's own mother, who was severely injured in the same incident that left him sickly and died few months later.
Bleach: A girl named Hisana was forced to find a way to survive in one of the worst districts of the Rukongai, so abandoned her baby sister Rukia to do it. Marrying Byakuya gave her the opportunity to search relentlessly for any sign of Rukia's fate, as she could never forgive herself for leaving her, but it's implied to have driven her to the sickness that ultimately claimed her life. Her dying breath was used to beg Byakuya to keep searching for her and adopt Rukia as his own if he ever found her.
Deconstructed in one case: Our Villain of the Week had a bad heart, but it was she who killed the loanshark who drove her boyfriend to suicide over the money for "that operation" (see Finger-Licking Poison for the murder itself). God, is she a bitchy chain smoker. In her confession, she mentions that her boyfriend was her Morality Pet and the only one who ever loved her after her parents' deaths. Be careful when threatening an Ill Girl's loved ones: if she gets better, she'll kill you! The other moral: in Real Life, being chronically sick can make a person pretty bitchy.
Played heartbreakingly straight in the fillers, with a girl named Kaori whose older brother Todakuro is the ghost writer to a murdered novelist, Daisuke Torakura, who paid for her hospital bills in exchange for the guy's hard work. We later learn the horrible truth: Kaori actually died a year ago because Torakura actually bribed her doctor into keeping her on painkillers only instead of paying for crucial and expensive treatment abroad (as per his end of the bargain), so Todakuro would remain indefinitely as his subordinate, which ultimately killed her. Then, Torakura maintained the lie via keeping Todakuro locked in his countryside villa, telling him that Kaori (supposed to be in an American hospital) was going to get better. When poor Todakuro found out the truth from the guilt-ridden nurse who used to tend to Kaori, he went nuts with pain and murdered Torakura. Asshole Victim seems a bit lenient.
Subverted with Kyosuke Haga's Missing Mom Chinami Shitara. She had an illness, and is been said that she fell victim to it a few years ago. More exactly, her brother-in-law Chuichiro caused her death because she knew too much about her husband Danjiro's death when he fell from the stairs, left him to die of his injuries and to stage it as a robbery gone bad. These incidents led to their son planning to avenge them by killing those who caused their deaths.
Chibi Marukochan: Koharu-chan, the intelligent Nagayama-kun's little sister, in most episodes is sick either at home or in the hospital. Koharu-chan is worried that she might have to repeat a year of school and be left behind by her classmates. Nagayama-kun and his classmates try to cheer her up. Maruko-chan drew an animation for her to enjoy.
Nunnally Lamperouge/vi Britannia, the younger sister of the main character, is both blind and contained in a wheelchair after she witnessed and barely survived their mother's brutal murder. He promises her that by the time she gets well, the world will be a better place. He never mentions how — to him, it doesn't matter how many people have to die or be manipulated to destroy the The Empire. Further, she didn't actually see it, having been a false witness due to a memory-altering Geass. Also, she gets better with time: in the series, she stays in a wheelchair but regains her sight (her father, Charles, geassed her into believing she went blind from the trauma of her mother's assassination) and becomes the Empress of Britannia, and in the Nightmare of Nunnally manga she heals completely and stays under the wing of Empress Euphemia Li Britannia.
Also, fellow student and revolutionary Kallen Stadtfeld/Kozuki uses the image of the Ill Girl to cover up her frequent absences from school so she can go play revolutionary. Maintaining the illusion limits her somewhat, but fortunately there's usually a distraction around to keep others from asking when she makes an unexpected display of physical prowess. Lampshaded in the 2nd Picture Drama, where Shirley grabs a naked Kallen from behind while they're bathing and comments on how Kallen is much stronger and athletic than she's supposed to be.
In the Cowboy Bebop episode "Waltz for Venus", Spike befriends a smuggler named Roco who is trying to earn enough money to pay for his blind sister Stella's eye operation. It ends in tragedy as despite Spike's best efforts, Roco is fatally shot. Stella is healed, but the first person she sees is Spike, which clues her in to her brother's death.
The Daughter of Twenty Faces: This is subverted quite quickly, in that the "ill girl" is in fact the main character who recovers quite quickly when taken away from the source of her "illness" by the eponymous Gentleman Thief Twenty-Faces.
Kaoru "Kaoru-no-Kimi" Orihara from Dear Brother was held back a year due to an unspecified illness, and when the story begins she has just returned to Seiran High School. As such, she not only hates it when people neglect their physical well-being, but sometimes collapses in fits of pain and needs both rest and painkillers. What's her ailment? Breast cancer, and she even had to go through a mastectomy at age 16, which caused her to break up with her then-boyfriend Takehiko (the titular Oniisama), and when she returned, she kept her illness a secret from most of her classmates until the symptoms of a possible relapse were shown towards the end. What happens to her varies according to the different continuities: In both of them she goes to Germany with Takehiko after they rekindle their relationship... but while she lives on and they stay Happily Marriedwith a child in the anime, in the manga Kaoru does die two years after leaving Japan.
Yuko Yoshida, the titular "Demon Girl" from The Demon Girl Next Doorwas one as a young girl, but her demonic awakening definitively took her out of this trope. Her experience with this trope, however, is an important to the universe's Backstory.
Ten years before Present Day, she was deathly ill due to curses on the descendents of Lilith. Her mother Seiko recalls she was "struggling with the respirator" at one point. Seiko implies it would have been fatal without Sakura's intervention, and when Yuko makes contact with what's left of Sakura in her memories, she tells Yuko it was even worse than Seiko thought.
What Sakura did was merely preventing her from dying, but for a long time her health was bad enough that her first few years of education were in the hospital.
Her friend Anri mentions that before her demonic awakening, Yuko often had to leave school early or miss it entirely because she was in the hospital so much.
Descendants of Darkness: Tsubaki Kakyouin aka "Tsubaki-hime" and Muraki's fiancée Ukyou Sakuraiji. We have next to none clues on Ukyou but we know that Tsubaki has an extremely weak heart, which led Muraki and other people to kidnap her Only Friend Eileen and then kill her to harvest her heart. When poor Tsubaki learns about this, shedoes nottakeitwell.
Hikari (Kari) Yagami in Digimon Adventure, younger sister of Taichi (Tai), who gets the Incurable Cough of Death during one episode. It's later stated that Hikari had not properly healed from a huge cold that left her bedridden and unable to join the kids who'd become the Digidestined in their fateful summer camp. Said cold came back with a vengeance when they were in the Digital World, causing Hikari to fall down with a fever that was just as bad as back home — only that in this particular Sick Episode, they had no ways to properly treat her, and for worse Machinedramon was tracking them. It triggered Taichi's bad memories of the incident in which, years ago, he accidentally caused Hikari to almost die of pneumonia. She seems to have grown out of this by the time of the sequel series.
Digimon Data Squad has Relena Norstein, which led to her older half-brother Touma (Thomas) joining sides with Kurata to get her "cured." This is a prime example of the writers not defining the disease: she's in a wheelchair, although she can walk short distances, and Touma wins the Nobel Prize for curing her, but it's incredibly vague otherwise.
A Dog of Flanders (1975): Alois comes down with a sickness in one episode (that is possibly related to the stress of her abusive father constantly manipulating her) and is so sick can't even leave her bed. Nello tries to visit her, but the Cogez family butler tells him that she isn't in a state where she'd like to be seen by him. She does, however, ask Nello to draw for her, and he does, even if he can't see her face-to-face in his frequent visits. Alois eventually gets better, and is happy to spend time with ber best friend Nello again.
Ruri from Dr. STONE is introduced as having been sickly most of her life. Senku manages to cure her.
Anemone has to live drugged to get away with the process she underwent to become Coralian-like, which causes her horrible side-effects like headaches, psychic nosebleeds and wild mental unstability. The doctor even says her resistance to the drugs was her greatest value. Ouch!
Female lead Eureka, as well. She spends much of the first half of the series feeling progressively worse due to her diminishing connection to the Nirvash.
Excel♡Saga: Hyatt is a particularly over-the-top parody of this, as she tries to go about her duties as an agent of ACROSS despite her tendencies to collapse, cough up contaminated blood (which kills small birds and sickens humans), faint, or even drop dead and then spontaneously come back to life. She always comes back to life, once even being charred to a decent crisp only to sit up later, as if nothing had happened. This appears to be an empathetic illness, at least in the manga. For several volumes Hyatt went some time without her usual blood and death routine, but the revelation that the competent Excel was an impostor brought it back.
Fafner in the Azure: Dead Aggressor: Shouko Kazama is the ultimate Ill Girl who suffers from some incapacitating disease that makes her a recluse of sorts. The trope is subverted though since her death is not caused by her illness, instead Shouko sacrifices herself for the sake of the island in a grand Heroic Sacrifice.
Ultear Milkovich was this in the past. Then she fell in the hands of a bunch of Mad Scientists whom her mother asked for help, not knowing about their intentions; they did heal the little girl, but they told Ur that she had died and then told their ex-patient that her mother had abandoned her... just so they could make the desperate Ultear their Dark Action GirlTyke Bomb.
Layla Heartfilia had been born with frail health and it contributed to her death when she had to use her own life energy to open the Eclipse Gate.
Rin Sohma suffers from stomach ulcers that originate from her Broken Bird personality and the stress of her horrible former home life. Despite this, she scares the living crap out of people with her headstrong and harsh personality.
Akito is another example - she suffers from an unclear illness, implied to be the one that killed her father, though it could also be psychosomatic. She's also the feared leader of the Sohma clan and an incredibly abusive person who is responsible for much of her family's dysfunction.
Fullmetal Alchemist: Subverted with Izumi Curtis. She's a pale, slender, and attractiveIron Woobie with frequent attacks of Blood from the Mouthas a result of having tried human transmutation to bring back her stillborn child, and losing her inner organs to The Truth as a result.. It's sometimes Played for Laughs when she coughs up blood on someone who upsets her, she can kick that someone's ass, bears' asses, and her husband's ass (for reference, said husband dwarfs her), and it generally need not be said that no one should just pity her, because she's so fierce. She does get better... though only in the manga and the Brotherhood series, as in the first anime she passes away in between the events of the Grand Finale and The Movie.
Protagonist Mitsuki Koyama has a cancerous tumor that prevents her from singing, and gives her exactly one year left to live. When she transforms into "Full Moon", she temporarily loses this tumor, and gains an amazing singing voice.
Notably Mitsuki's mother and grandmother were both ill girls in the manga. Fuzuki (the grandmother) was shown to be very sickly in her youth, though she apparently to grew out of it. Hazuki (the mother) is implied to be an ill girl in a flashback when it is stated by Fuzuki that she isn't healthy enough to have a baby after Hazuki announces her pregnancy.
Mitsukake's girlfriend, Shoka, died from an illness and he was too late to save her. At the time, Mitsukake was dedicated to healing and medicine, and Shoka's death caused him to give it up out of regret. She Came Back Wrong later on, forcing Mitsukake to Mercy Kill her.
Fushigi Yuugi: Genbu Kaiden has Takiko Okuda and her Missing Mom, Yoshie. Takiko caught tuberculosis from the deceased Yoshie while tending to her in her own world. She insists it's just a cold, as her father makes plans to take her back to Tokyo for medical treatment.
Lita is a girl who is in a wheelchair whom Hayato meets in the Peruvian GP. She recently has surgery for her legs, but she's afraid to use them despite them being completely healed. After the race, she gets up thanks to the courage he gives her.
Elena is the daughter of the orangizer of the Fireball Race and has a weak heart since birth. During the race, she has a seizure while navigating with Hayato and as it worsens, he calls in HSR-III to take her to the hospital. She gets better at the end of the episode.
An episode has an ill Mint in a hospital while watching the leaves on a tree — she hopes to live long enough to watch a leaf fall off — and it promptly does, at which point she notes she was referring to another leaf, which also falls off. As she tries to refer to a third leaf, all the leaves are blown off by a strong wind.
Another character, Chitose, is an obvious parody, claiming to have been confined to a hospital most of her life. More likely it's another product of her attention whoring; she was enough of a Scrappy in the game that even the anime writers didn't like her, and her personality was exaggerated to that of a wangsty histrionic (although to be fair, everyone else was exaggerated too).
Gangsta.: Veronica is the mysterious Twilight woman that once resided at Benriya with protagonists Nicolas and Worick. It appears she overdosed on the Cereber drug and became terminally ill, at one point while visiting a brothel Alex sees (through a partly closed door) Nic possibly tending to Veronica on her sickbed. Whoever she is or whether she’s still alive, Nic appears to have had a close relationship with Veronica and flashes back to her sometimes when interacting with his new Love Interest Alex.
Get Backers: In the second season, one of Ban and Ginji's missions is to get a very rare type of blood (named the "Bombay Blood") for an Ill Girl named Yumiko, who needs an urgent transfusion or she'll die in few days. It turns out that Akabane has a dose of it and they have to fight him and his partner Maguruma. It's also revealed that Ginji had an Ill Girl friend in the Infinite Fortress days and she died due to lack of treatment, so he's determined to not fail again for Yumiko's sake. They get the Bombay Blood, and Yumiko is saved.
Four Murasame from Zeta Gundam. As a side effect of the experiments and treatments she's been subjected to, she sometimes suffers extremely serious migraines; when that happens, the poor girl ends up almost unvariably on the ground/floor, either whimpering or screaming in utter pain, and needs medicines to get rid of it.
Played with in Gundam X. Female lead Tiffa Addil is a Fainting Seer and kinda delicate, but this doesn't stunt her that much. Her only brush with death was actually a side-effect of her being poisoned by one of the villains.
Stella Loussier from Gundam SEED Destiny. Being one of the Extended, her life hangs on by treatment in the Alliance medical rooms and she will die if she doesn't get it, which is shown in her seizures and memory gaps. For worse, the training has damaged her mind as well, and she's few more than a very childishOphelia almost unable to function in real life when outside missions. Yeah, it sucks to be her.
Gundam 00: Louise Halevy in the second season. To start, Louise lost her left hand in the bombing incident that decimated her family in the first season. She got said hand back through an undisclosed medical treatment and Took a Level in Badass that led her to become a Dark Action Girl, but she also had some very ugly seizures and had to pop some pills. Her sanity continued slipping as the series advanced, but luckily, by the end she starts getting better. In The Movie, she's mentally doing better but still in physical recovery.
Lu Anon from Gundam AGE is a tragic non-combatant example. A Vagan girl who is Kio Asuno's age, she suffers from a terminal disease due to exposure to Mars Rays. In the little time she has left, she wants to live happily and normally, especially after she meets Kio. The time they spent together and her heartbreaking death became major turning points in Kio's attitude towards the enemy and the war.
Gunslinger Girl: All the girls will meet the same fate, since their lifespan is immensely shortened due to their cybernetic implants and the side effects of the conditioning drugs they have to take. More specifically:
Rico turns out to have been an Ill Girl prior to becoming a cyborg, languishing away in an hospital after her parents simply abandon her there to her luck until she's taken in by the organization.
Angelica is the first of the girls to be graphically shown breaking down due to conditioning sickness.
Claes stops taking roles in missions not just because of her trainer Raballo's death, but because she actually has a weak heart.
Elisabeta, a Chernobyl survivor and former aspirant ballerina who developed cancer and tried to commit suicide after her cancerous leg was amputated. Then she was brought into the Agency and became Petrushka aka Petra. At the end of the manga, her cancer returns in the form of leukemia, but she dies peacefully, unlike many of the other girls.
Alitta from the Netherlands arc. Fortunately, it's a temporary illness rather than a life-threatening one. Unfortunately, she's a famous stage actress and thus she needs her Identical Stranger Lunlun to be her temporary Body Double...
Lucero, the little girl from the Orphanage of Love in the Italy arc, who's blind. Her friends decide to search for an old treasure buried near the orphanage to sell it and get the money for the orperation. The treasure is actually an old bomb.
Haou Airen: One of the two reasons why Kurumi Akino is the main breadwinner of the family is that her mother is an ill girl and thus she cannot take a regular job. The other is that Kurumi's Disappeared Dadperished two years before the story started. When Hakuron abducts her and takes her to Hong Kong, he promises to send Mrs. Akino and her remaining kids enough money to sustain themselves without Kurumi's help. (And as far as the audience knows, he sticks to his word.)
HappinessCharge Pretty Cure!: The Movie has a wheelchair-bound character, Tsumugi-chan, who was a ballet student before something happened that paralyzed her.
Harukanaru Toki no Naka de; Inori's older sister Seri is sickly, leading to Inori having a Big Brother Instinct towards her, despite him actually being younger. A flashback in the Hachiyou Shou TV anime reveals that this is part of the reason Seri got close with Iktidar, who saved her when she was threatened by several men while helpless from her condition. Somehow, being an Ill Girl didn't stop Seri from having Ikutidaru's baby.
Hikaru No Densetsu: Shiina Hazuki was this in the manga. Her Olympic abilities were severely impacted by her aplastic anemia, and she was constantly in and out of hospitals as a result. In the anime, this is downplayed as she goes to the hospital (it's not specified what exactly for) and she mentions there are a lot of obstacles to her becoming a gymnast.
Marie was confined to a wheelchair, but starts to walk after befriending Lundi.
Jeudi's Missing Mom Helene suffered from a weak heart and almost total blindness after the accident that separated her from Jeudi. It's horribly subverted: the villain Toulonchamp and his daughter Mathilda have been slowly poisoning her for years so they force her parents to collaborate in their schemes.
Zigzagged in I Got My Wish and Reincarnated as the Villainess (Last Boss)!. There's no doubt that Elizabeth was a sickly girl in her previous life and spent her entire life in the hospital, and the first scene follows the conventional portrayal of the death of a consumptive heroine, being very depressing as well as her spent a significant part of it lamenting her condition. She was also, at a minimum, generically cute with no physical signs of being a chronically bedridden person. That said, the second scene establishes her, while kind, is also a Determinator, making her a subversion of sorts in that she isn't delicate in spirit.
Idaten Jump: Kiku, also Kouhei's little sister and the local Yamato Nadeshiko, suffers from an illness that turns out to be a consequence of the disbalance between the X Zone and Earth. Once it's fixed she starts to get better.
Idol Densetsu Eriko: Fuyumi is a 12 year old girl who adores Eriko's music, but has an unspecified illness and has to be admitted to the hospital as a result. She is happy when Eriko sings for her from the rooftops.
Ikki Tousen: Subverted. Ryoufou Housen is dying of an undisclosed illness, but she's still a fearsome Dark Action Girland actually goes down fighting. In the anime, she getsbetter later, though that also included some Laser-Guided Amnesia... and dying again in the end.
Kikyou took this role more than once, despite being undead. Namely, it happened every time she was either weakened by poison or suffering the physical downsides of her clay body.
Jotaro's mother Holly Kujo from Jo Jos Bizarre Adventure Stardust Crusaders is one. In her case, she's a Stand user, but unlike her family, she lacks the fighting resolve necessary to maintain a Stand properly, so she ends up falling ill from a power that's slowly sapping away at her life-force. The entire reason why Jotaro and his friends go after DIO is so they can cure Holly, as DIO's resurgence partially caused her situation with her Stand going haywire. Once DIO is defeated, Holly gets better. What makes it strange is that several other characters survived manifesting Stands, including multiple animalsnote Iggy, Forever, Pet Shop, Stray Cat, Coco Jumbo, and Foo Fighters, two babiesnote Mannish Boy and Shizuka Joestar, a sentient swordnote Anubis, and several childrennote Ken Oyanagi, Emporio, Daiya Higashikata, and Tsurugi Higashikata; Polnareff and Kakyoin also had their Stands as children.
Jo Jos Bizarre Adventure Jo Jolion has Holly's Alternate Universe counterpart, Holly Joestar-Kira. A former opthamologist (i.e. an eye doctor), she ironically ends up hospitalized for some strange mental issues, which included loss of memory and other eccentric behavior, like mistaking a nurse for a pair of boots. The truth turns out to be far more complicated: She's a a first-born daughter of a branch of the Higashikata family via her ancestor, Rina Higashikata. Unlike sons, who get symptoms at age 10, daughters begin displaying symptoms of the mysterious stone disease later in life. Holly's son, Yoshikage Kira, began noticing her memory loss and other symptoms, and presumably excised parts of her brain and other organs that began to turn to stone with his Stand, Killer Queen, as she doesn't have any external scarring. For a proper cure, Kira sought out the Locacaca from the Rock Humans with Josefumi's help, thus spurring the entire plot of JoJolion due to the result of the heist. Later on, however, it's revealed that she was actually experimented on by the Locacaca Research Group with Locacacas, which may be the real cause of her illness, rather than the Higashikata Family's Rock Disease.
The King of Fighters: Kikuri Tanima from The Sun and the Moon ~ PrologueRadio Drama is the sister of Iori Yagami's bandmate Konoe, and she suffers more than one seizure during the drama — one of these lands her in the hospital. And she does not get better... in fact the CD drama is a Whole Episode Flashback, and Kikuri has already been dead for at least five years.
Fujimiya Aya fills this role for most of the story after she's hit by a car and ends up comatose, prompting her older brother Ran to become an assassin to pay her hospital bills — and to actually assume her name in tribute. She ultimately gets better.
In one episode, Ran encounters another girl whose brother has entered a Deadly Game to pay her medical bills.
Lady!!: Lynn's half-sister, Sarah Russell, has always had a very frail health. She has to be homeschooled since she often spends her days feverish in bed, and once in a while passes out if she's too stressed. All of this messes up badly with her self-esteem, and at first she's rather mean to Lynn out of fear that, since Lynn is The Cutie, everyone else will like her better.
Mutsumi has a severe case of anemia and passes out almost everywhere; one reason why she keeps failing her college entrance exams is because she faints in the middle of writing them. During her Crash-Into Hello with Keitaro, she falls over, with Blank White EyesandBlood from the Mouth. Keitaro checks for a pulse...and there isn't one. Cue Freak Out. She gradually gets better, but it seems her fainting spells are closer to actually dying then "normal" fainting.
Naru used to be sickly as a child. She has asthma, and while she's mostly fine in teenage/adult years, in her childhood her attacks were much more serious. Several years ago, Naru's parents sent her to Hinata Sou hoping that she'd recover due to the zone's benign climate, but she was very lonely and depressed. That was the time when she befriended two older kids, Keitarou and Mutsumi, and the three made The Promise.
Kanata, Konata's mother and Soujiro's wife, was apparently sickly in life and died early on of an unknown illness. That, and the couple being childhood friends and Kanata being older than she looked, makes Konata remark that her parents' relationship sounds like a storyline from a Dating Sim.
Yutaka, Konata's paternal cousin, has recurring (albeit mild) health problems that make it difficult for her to keep up with her friends — she was nearly rendered a Broken Bird from the social isolation caused, and she hates making people worry every time she gets sick. And her case of Older Than They Look is even more severe than Kanata's...
Hayate Yagami in Magical Girl Lyrical Nanoha A's. However, in the sequel series StrikerS, she is completely healthy. This because her "illness" was actually the curse of the Book of Darkness, so once the Book was destroyed she was able to recover.
Professor Granz Florian from both the game and movie continuities is suffering from a terminal disease that will kill him before his dream of restoring his planet's dying ecosystem will show any results. He dies in both stories, though Yuri's intervention means that he at least holds on long enough to get confirmation that his life's work will be completed by his daughters.
Magical Project S: Parodied. One of the Love-love Monsters is called "fake sick girl", who even gives the speech about not seeing the last leaf fall from a tree. When the person talking with her mentions that the tree is quite full and healthy, she blows it up with a cannon hidden in her bed.
Marmalade Boy: Anju Kitahara in the anime version has a weak heart and might not live for long if she doesn't go through a very dangerous operation in the USA, but she attempts to remain cheerful and befriends her beloved Yuu's girlfriend Miki, telling her that she won't break them up and is as happy as she can with being Yuu's Unlucky Childhood Friend. She's operated and gets better, and when Yuu breaks up with Miki she has a small chance to get Yuu for herself, but ultimately she (and Miki's other love interest Kei) give up when they get back together.
Mermaid Melody Pichi Pichi Pitch: Michal Amagi is a Tomoe Hotaru-esque figure that also happens to be Lucia's romantic rival and the little sister of one of the villains. It's a wonder she survives, really.
Millennium Snow: Chiyuki has a heart condition and isn't expected to live for too long. Then, she becomes the blood source of the local vampire Tooya, which extends her lifespan to match his own.
My Daddy Long Legs: Leonora Fenton seems to have classic symptoms of tuberculosis of the lungs. It's actually a heart condition that gets corrected by surgery.
Negima! Magister Negi Magi: Ako Izumi briefly fills the role after she catches some sort of disease upon arriving in Magicus Mundus. It varies a little bit in that she gets the cure early on, but it's so expensive that it forces her and two of her friends (Natsumi Murakami and Akira Ookochi) to sell themselves into slavery. This in turn leads to Negi having to enter a tournament to win the money to buy their freedom.
Neon Genesis Evangelion: Toji Suzuhara's off-camera sister suffers injuries as one of the civilians caught in the middle of the fight in the first two episodes. Toji is eventually recruited as the pilot of Unit 03 in exchange for her being transferred to NERV's medical facilities. However, Toji himself is severely crippled when an Angel takes over his Eva. In Rebuild, we get to see Toji doting on his little sister as she finally gets out of the hospital, and Asuka ends up piloting Unit 03 in his place.
One Piece, quite a few actually, mothers especially bite it:
Usopp's best friend Kaya from is very delicate young woman who goes through quite the Break the Cutie. She got better later, though.
The same can not be said for Bachina, Usopp's mother who died of her own illnesses despite her son's best efforts to cheer her up. This likely made Usopp strive to get Kaya better.
Nami falls ill after Little Garden, when she's bitten by a prehistoric bug. As a consequence, she gets a dangerously high fever and the journey to Alabasta must be put on hold as they find a doctor. Though that meant Luffy and Sanji must take her up a freezing cold Death Mountain, Nami is cured just in time: according to Dr. Kureha and Chopper, three days later she'd be dead.
Senor Pink's wife Russian became a catatonic Empty Shell after a brutal Break the Cutie process that included the death of their baby son Gimlet, her finding out her husband wasn't a traveling businessman but a pirate (aka the type of people she despised the most), and suffering brain damage after being caught in a landslide. She could only smile when Pink dressed up like a baby, and in the present she's strongly implied to have died of a broken heart and bad health.
Vinsmoke Sora, Sanji's mother, made herself sick as a side-effect of a risky gambit she took. As her husband Judge genetically modified her quadruplet sons while they were in her womb, so that they'd be souless killing machines, Sora desperately tried to counter this and took a drug to nullify the changes; as a side-effect her health took a nosedive from then on, but she was overjoyed to see that Sanji had turned out decent (though his brothers couldn't be saved), and doted on him and his sister Reiju before passing away.
Penguindrum: Himari Takakura's illness isn't exactly clear, but it seems to be due to a weak heart. In fact, the plot is kickstarted when she dies and is revived in the first episode. And it won't be the first time she kicks it.
Planetes: Subverted; during a hospital stay Hachimaki meets a girl who he believes to be chronically ill, but does not want to be rude by asking. In reality, she is a child who was born on the moon, and is staying in the hospital to provide medical information to scientists and doctors.
Homura Akemi, before meeting Madoka and her friends, was this. She spent most of her life in the local hospital due to a severe heart illness. It's not specified how she got rid of it, but most likely did it with her Magical Girl powers. This is also the basis of her attitude towards Madoka, as her social isolation and orphanhood means the latter is the first and only friend she could made for the past 14 years.
Also, according to popular Fanon, Nagisa Momoe, who became Charlotte the Dessert Witch, may have been one when she was still a Magical Girl. What prompted this Epileptic Tree was that her Grief Seed first appeared outside a hospital, there is a general medical theme to her barrier as well as the sweets, and the fact that she's obsessed with cheese, which chemotherapy patients aren't allowed to have. Add in the detail that Kyubey has contracted girls on the verge of death at least once (see: Mami, who had been seriously injured in the car crash where her parents died), and this theory became popular.
According to Word of God, Nagisa's mother turned out to be this, as she was dying, and Nagisa's wish was to share a cheesecake with her mother before she died. Whether or not Nagisa was also ill has not been specified.
Reborn! (2004): Chrome Dokuro/Nagi will die if Mukuro or Daemon Spade isn't giving her illusionary organs to replace the ones that she lost when she was hit by a car.
Remy: Nobody's Girl: Arthur Milligan was born with an inability to walk, and moves from Britian to Toulouse, France, to seek treatment. There he befriends Remy, and she often helps him move around by pushing his wheelchair.
Rozen Maiden: Megumi aka Megu, Suigintou's medium and Morality Pet, is bedridden from an illness. She has extremely low self-esteem as a result, and Suigintou sorta empathizes with her.
Sailor Moon R: Anti Villainess An occasionally fell into the archetype, getting tired and out of breath easier than her "brother/lover" Ali/Seijuuro. Although in An's case this was caused by her starving, since she refused to eat regular food like Ali did, and humans' life energy wasn't available every time she needed it.
Hotaru Tomoe, who suffers seizures and cannot make huge physical efforts. She more than once ends up collapsing in the streets.
One-time character Misa-chan from the Stars season, an hospitalized little girl who bonds with Taiki/Sailor Star Maker.
Saki Achiga-hen: Toki Onjouji has a tendency to faint at any given moment. Meanwhile, Yuu Matsumi gets chilled very easily to the point where she has to wear a cardigan, mittens, and a muffler even during the summer.
Satou Kashi no Dangan wa Uchinukenai: Mokuzu Umino claims that her painful limp and clumsiness were caused by a witch's spell that turned her into a human with an imperfect pair of legs. She says this same spell will turn her into sea foam in one month's time if she does not fulfill her wish of finding a "precious friend". She also must drink copious amounts of water before speaking or exerting herself in any way. No one takes her claims seriously, though. It turns out Mokuzu's been abused by her father Masachika for years: her limp is due to a hip injury received as a baby, and to top if off, she is deaf in one ear due to her dad's beatings as well. And even worse, she is later beaten to death by him.
The Secret Garden: Colin Craven is bedridden and needs a wheelchair to move. He's initially very sour and aloof, but Mary encourages him to still be happy despite his handicap, and invites him to hang out with her and Dickon.
Sekirei: Chiho, Uzume's Ashikabi, has a mysterious unnamed illness that keeps her hospitalized. It later becomes a pivotal plot point towards the middle of the second season (Pure Engagement).
SHUFFLE!: Asa Shigure suffers a mysterious illness that often leaves her bedridden, and starts becoming worse as time passes. It's not an illness, but Power Incontinence: her weak half-demon body cannot handle the strong magic inherited from her mother, the demon Ama, but Asa utterly refuses to use said power because Ama suffered horribly due to them, thus Asa doesn't want her mother to be sad. Rin has to take a VERY risky third option to force her release said energy, and almost dies for it.
Someday's Dreamers II: SoraSora seems to be mostly in good health, having little trouble with physical exercise or performing straining magical rituals — until she suddenly appears to have been suffering from a terminal heart condition for a while already, leading to a severe mood whiplash in the series.
Tekkaman Blade: Miyuki Aiba/Shana Carter, aka Tekkaman Rapier/Teknoman Shana, is a very cruel version. She's actually a Tekkaman whose transformation process was incomplete, therefore she suffered horrible pains and her lifespan was dramatically shortened. She chose to go down fighting and perform an Heroic Sacrifice than die of her illness.
Tenchi Muyo!: In The MovieTenchi Forever!, Haruna is this. After fleeing with her lover, Yosho/Katsuhiko, she became ill during their trip. She died before the couple arrived on Earth.
Kosumo Koganehara was born with a a weak heart. In fact, the manga starts when she has a seizure during her treatment in the USA and needs an urgent transplant, but her extremely rare blood type doesn't allow for an easy one. The donor that saves her life just happens to be Himiko, a Miko and Magical Girl Warrior who has just died via an Heroic Sacrifice to save a child, so Kosumo inherits her powers alongside her heart and blood and must take up her demon slaying mission — with the help of Himiko's Tall, Dark, and Handsome guardian, Hitsuji.
Later on, the 98th Himiko, the one who came before the aforementioned Himiko we know. She was a fellow Miko who died of cancer when the 99th Himiko was 10-years-old, which wasn't helped by her already suffering of a years-long depression and being separated from her bodyguard and lover, Hishou.
Vampire Princess Miyu: Subverted quite cruelly with Aiko. She was thought to be in a Convenient Coma due to either illness or Demonic Possession, but Himiko later discovered that she summoned the main Shinma in despair after blaming herself for her parent's deaths, having survived the accident that caused their deaths. Ever since then, she lays on her old futon located in her her decadent Big Fancy House and simply... sleeps, while the Shinma wreaks havoc around. She only wakes up when Himiko confronts the Shinma, but Miyu stops her when she's about to drink Himiko's blood, and once the Shinma is defeated, Aiko dies.
Vampire Yui: Subverted. It's believed that Yui is an Ill Girl with severe anemia, but the truth is that her Guardian powers have just awakened and, since she had no real idea of what was going on, she missed the blood "meals" she needed (which is not helped by how Yui at first refuses to drink blood from humans if she can help it, so her Battle Butler Nagi gives her his blood instead).
Kotori Monou has a serious heart condition. One of her older brother Fuuma's first scenes in the manga has him reading out loud a list with the remedies that Kotori has to take that day.
Venus to Mamoru!: Parodied and played melodramatically. During the Valentine's Day episode of the anime adaptation, a contest is on to see who can give Mamoru chocolate in the most creative way possible. Shione orchestrates a "Last Leaf" situation with her brother claiming her lack of fashion sense is a disease affecting "one in six billion people" that will kill her. In the end, Shione "dies", but not before giving Mamoru her chocolate...shaped like her hairstyle.
Kousei's mom, Saki, already passed away from illness before the series began. Even more unfortunately, Saki's emotional state upon being diagnosed became so bad, she turned into a mix of Abusive Parent and Education Mama to Kousei, pressuring him beyond his limits in an horribly misguided attempt to make him both perfect and self-reliant.
Kaori Miyazono is one as well. It's first hinted in Episode 4 (when she collapses after her performance) and further shown in Episode 9, when a lot of pills can be seen in her bag. Then in Episode 15, her legs give out in the middle of the hospital hallway at night. And in Episode 16, her arms can't hold up her bow or, at the very least, a bottle of juice Kousei hands her. While her disease is unnamed, it's explained that she will lose control of her legs and her limbs and suffer from seizures that will lead to heart failure; most fans have suspected that due to the symptoms, she and probably Saki too suffered from Amyotrophic Lateral Sclerosis aka ALS. And Kaori dies from the illness too.
Shizuka Kawai (a.k.a. Serenity Wheeler), prior to her operation. Her condition depends on the adaptation - the first anime series gave her an unspecified disease, but in the manga and second anime series, she's going blind.
It turns out that Pegasus's Freudian Excuse was centered around one of these: his deceased fiancée and Victorious Childhood Friend, Cecilia, died of illness few before their wedding.
Zetsuai (1989): Madoka Shibuya is one who serves an important part in the Back Story. Madoka was both a Kouji fangirl and the already fatally ill daughter of the president of Kouji's record company, and he had a Pet the Dog moment by visiting her before she kicked it. Her older brother, Katsumi, decided to repay Kouji's kind action by becoming his manager.
Coach Jin Munakata from Aim for the Ace!. The reader knows what he has: leukemia. And unlike others, he actually dies.
Sho from Arrietty. He tells Arrietty he has always been ill and can't play with other kids. The reason he is currently staying at his aunt's place is because he is getting an operation on his heart.
Dr. Kuro Hazama aka the title character of Black Jack, thanks to the hidden field mine that went BOOM on him and his mom, killing Mrs. Hazama and severely injuring him. Of coruse, he also attends many ill boys and girls as well; in fact, regular character Sharaku was introduced as one in the newest series, since he and his sister Wakou join the cast after BJ has to operate on him in the first episode.
Captain Jushiro Ukitake has been suffering from tuberculosis all his life, which makes him spew blood if he exerts himself too much, turned his hair white, and causes him to spend most of his time in bed. (Although since he's over 2000-years-old, it's obvious he isn't dying from it... Unless he's dying very, very slowly). 616 explains that he should have died when he was young, but thanks to his parents's pleas to a local god named "Mimihagi-sama", he survived... but in exchange for his life, his lungs suffered badly. Hence, the Incurable Cough of Death and Blood from the Mouth he's been plagued with throughout his whole life.
As Nodt from the Vandenreich turns out to have been this in the past. A flashback reveals that before he met Yhwach, he was but an ill, bedridden man, barely able to breathe and fearfully awaiting his death while simultaneously proclaiming how he hates living like that. When Rukia finally slays him with her Bankai, his last thoughts are filled with this old fear.
In Bokurano, Kunihiko Moji's best friend Nagi is an ill boy with a weak heart and is hospitalised when the plot rolls in. Moji, who has signed up to pilot a Humongous MechaPowered by a Forsaken Child, wants his own heart to be harvested and given to Nagi for a transplant once he kicks it. This is fulfilled and Nagi gets better.
A Bridge to the Starry Skies has two of these: one is the protagonist's little brother and the other a random village kid.
Bungo Stray Dogs: Akutagawa Ryunosuke is very underweight, has a sickly appearance and frequently coughs, and a special spinoff even has him introduced as the “Prince of the School's Hospital Wing”. It's likely a Shout-Out to the author he is named after, who was psychically (and mentally) unfit for most of his life.
Since this is a series about sports, there aren't many boys with bad healths but their "places" are generally taken by characters who have serious game breaking injuries at some points and cannot play at full potential, lest their wounds will get worse and put their careers at risk. Some examples of this subversion are: Wakabayashi and the aforementioned Misugi in the first part of the manga; Wakashimazu and specially Tsubasa himself in the second part of the manga and in Shin; Wakabayashi again, Misaki and the South Korean captain Cha Inchon from the World Youth Cup manga.
Eisuke Hondou's important backstories were all when he was hospitalized; first due to leukuemia and then due to accident. In the first case, he was saved due to his older sister's marrow donation, which changed his blood type and tipped Conan/Shinichi off in regards to said sister's own identity and role.
Seiji Asou from the Moonlight Sonata case used to be this as a young boy. In fact, when he was hospitalised in Tokyo, his family (including his father, a famous pianist) was killed in strange circumstances, related to the authorities from the island he grew up in and the shady dealings they had with his dad. For the rest of the story, see Harmless Lady Disguise.
In a filler case, the Detective Boys and Conan go to an hospital to visit their classmate Jun Kataoka, who is so ill that he'll have to stay hospitalised for weeks. Since Jun is also Conan's Identical Stranger, at the Detective Boys's suggestion they swap clothes and places for a day. And then Conan is abducted by a mysterious man who wants to blackmail Jun's very rich widowed father and his soon-to-be stepmom, but he manages tp escape. And then, the kidnapper appears dead...
The whole sixteenth movie, The Eleventh Striker, had one of these as motivation: The Big Bad and Anti-Villain was a man who had an Intergenerational Friendship with an ill boy named Tomofumi Motoura. Poor Tomofumi who died years ago when he was in need of medical attention but a soccer mob stopped the ambulance he was in and prevented the medical staff to save his life. (And a drunk Kogoro was a member of said mob, too.) So the Big Bad became a Mad Bomber hell-bent on revenge against both Kogoro and anything related to soccer...
Rosette Christopher's brother Joshua in Chrono Crusade was plagued by constant seizures when he was a child — made even more frustrating by the fact that they came alongside healing abilities that were completely ineffective on himself. It's this that drove him to accept Chrono's horns from Aion, completely unaware that they would drive him completely insane.
Classi9: Chopin is sick so often that Liszt knows exactly what to do when someone else gets sick and the cast uses his personal pharmacy when Ren gets a cold. His weak constitution isn't helped by his Performance Anxiety and he already passed out on stage before chapter 7, which takes a toll on his health. Truth in Television as the real life Chopin's cause of death is still debatable because ther are doubts on which illness finally killed him, he was also sick a major part of his life and did prefer small and cozy venues to big concerts.
Subverted in Code Geass R2. Lelouch's opponent and later ally Li Xingke has an Incurable Cough of Death and might not live for long, but remains an excellent pilot and strategist. He makes it to the end of the series, but it's hinted that he may have passed away after the Zero Requiem.
An ill baby boy is Ivan Whisky aka Cyborg 001 from Cyborg 009. His enhancements somewhat cure or slowen his illness, but he's now trapped in the body of a baby forever. On the other hand, he's now a very powerful psychic.
Den-noh Coil, which seems to enjoy gender-flipping a number of traditional shonen anime roles, has a sick boy in the form of Harakawa Kenichi aka "Haraken." He suffers from fainting spells and some kind of poorly-defined heart flutter that may or may not have to do with his investigations into the mysterious Illegals.
Son Goku himself for most of the Android Saga in Dragon Ball gets sick with the heart virus a unexplained disease that can weaken and kill even a Saiyan like him. In the worst timing, Goku starts feeling the effects just as he’s fighting the new Android threat and has to be saved by Vegeta when the pain in his chest weakens him to point where he can’t fight. Goku then spends most the saga in agony in bed with a despairing Chi-Chi looking after him, thankfully thanks to Future Trunks to providing a antidote from his future Goku is saved and eventually recovers... before dying (again) in a Heroic Sacrifice to stop Cell blowing up the Earth.
In Fate/Prototype, the preliminary version of Fate/stay night, there is Isemi aka the Third Master. He's a bed-ridden pre-teen boy, kept alive only by medical machinery after having been subjected to horrible experiments. Isemi uses his Command Spells to fully incarnate Rider in this world right before dying, and after he kicks it Rider wants to use the Grail to revive him.
Toki is incredibly sickly due to radiation poisoning he received sacrificing himself to get Kenshiro and his fiancée Yuria into the nuclear bunker in time before the bombs hit. Despite his condition Toki is still surprisingly capable of kicking ass as a Weak, but Skilled fighter, and would’ve been the successor to the Hokuto Shinken had he not become ill.
Rei becomes this after Big Bad Raoh strikes his Shinketsushū vital point giving him three agonising days left to live. Determined to go out in style, Rei has the aforementioned Toki painfully extend his life for one more day allowing him to avenge his Love Interest Mamyia by killing her former captor Yuda and succeeds in doing so before succumbing to his fate.
Akira Sohma, Akito's father in Fruits Basket. He had an unnamed illness, which may have been compounded by the stress of being Head of the Family, and by the time the series starts he's been dead for years.
Yuki was sickly when he was little, too, as evidenced by his persistent cough. It's mainly just asthma, though, which he eventually outgrows.
Takuto Kira from Full Moon is revealed to be a former ill boy. Like Mitsuki he had a cancerous tumor in his throat which lead to the end of his career as a singer. Also like Mitsuki he refused the operation that would save his life on the grounds that it would render him mute. In the manga he was given the operation anyway and the loss of his voice lead him to commit suicide The final volume of the manga reveals that he survived and he had been in a coma ever since. In the anime he drove his motor cycle off a cliff shortly after being diagnosed. He ends up back from the dead in both versions.
Uruki's father Temudan had always been sickly, and by the time the series begins his illness was so bad that his limbs were replaced with prosthetics
Temudan's subordinate Urumiya Hagas isafflicted with a similar illness that is about to kill him. He falls in love with Temudan's niece Firuka because she tookcare of him, and he ultimately brews a Self-Sacrifice Scheme to both die and give the powers of the Urumiya Senshi to his twin younger brother, Tegu.
Tomokane's older brother in GA: Geijutsuka Art Design Class. He apparently spent more time in the nurse's office than his own classroom, to the point that teachers fear his attendance would be the major obstacle in college admissions. He and his Bokukko younger sister make an (uncordial) example of Sibling Yin-Yang. He also exploits this trope to avoid punishment from, say, mentally bullying his sister as he's often seen to be too frail to be physically punished.
Gargantia on the Verdurous Planet has Bebel, younger brother to Amy. He has some sort of lung problem that keeps him mostly bedridden, and otherwise he's usually in a wheelchair to keep from overexerting himself. Part of Ledo's character growth comes from realizing that back in the Galactic Federation, Bebel would have been summarily euthanized like Ledo's own brother.
In the manga The Gentlemen's Alliance, the real Shizumasa Togu was an ill boy and being unable to attend school he makes his twin brother go in his place. Later chapters reveal that Shizumasa had Leukemia and had been refusing to get a life saving bone marrow transplant as he wants to die so that his twin Takanari can take his rightful place as the family heir (their family holds a test to determine the next head and when the twins took it as children, Shizumasa cheated out of fear of what would happen if he lost the test and ended up winning. However as a result Takanari was badly injured and Shizumasa would regret his actions from that point on). When Takanari learns this he gives up on his grudge against his brother and goes to the hospital to give Shizumasa the transplant he needs.
Heart Catch Pretty Cure has a very interesting case — Itsuki Myoudouin's older brother Satsuki is a case of Ill Boy and a Heir to the Dojo. With him sick, Itsuki's determined to take over their grandfather's dojo, leading her to become a Wholesome Crossdresser because she thinks she won't be taken seriously otherwise. It isn't until halfway through the series that Satsuki goes through an operation and is cured (though it's a pretty risky surgery that could've potentially killed him), leading to Itsuki to start abandoning her role, openly embrace her love for more girlish things and be the Third Precure.
England takes up the role briefly in the episodes featuring The Grim Reaper.
Spain, when his economy is in a terrible state and he gets a cold because of it.
According to Word of God, Austria spent some years in a wheelchair. It's not explained when this happened, but fanon speculates that it may have taken place either after the dissolution of the Austro-Hungarian Empire or right after World War II.
Friederich Brandel from Honoo no Alpen Roseaka Jeudi's Disappeared Dad. In a subversion, a good part of his horrible health comes as a consequence of a terrible accident he was involved into... and he dies of it, right after having been reunited with Jeudi.
Innocents Shounen Juujigun subverts this with Etienne's companion Remy, who has the kind and gentle personality to a T... but his illness is Hansen's disease aka leprosy, which has Body Horror-like consequences on him and forces him to cover his body with bandages. He joins the Children's Crusades in hopes of finding a cure, but his health keeps getting worse... By the time he dies his body is literally falling apart, as seen in how his nose is missing and his face has rotten away.
Kenneth "Ken" Robbins from Kaleido Star. His dream was to participate in the Kaleido Stage as one of the acrobats, but since he got a weak heart, he mostly does staff job. Later in the series, he does some acting as well, but not with any life-risking acrobacies.
Yayoi from Loveless, which seems to be the result of severe athsma.
In the Magic Kaito special Tears of Love for the Black Knight (based on a story from the fourth manga volume), FBI agent Jack Connelly's son Kenta is one of these, and he needs surgery to get better. His father is so desperate to get enough money that he becomes a thief named Nightmare so he can gather cash and Kenta can be operated on. At the end of the special Kaito Kid confronts Jack on how not only he's a "newbie" in regards to classy thievery, but on how this whole deal will badly hurt Kenta if he ever finds out, and attempts to get Jack to quit... It endsin tears.
Eagle Vision from Magic Knight Rayearth has overused Autozam technology (powered by mental energy), giving him anemia-like symptoms. He later reveals that he is dying from it, but he starts to recover in Cephiro in the manga.
Nikaidou from March Comes in Like a Lion. He has an unspecified illness that often manifests in the form of anemia. It's frequently mentioned by members of the cast, and is something of a minor sub-plot involving him.
After's Kamille Bidan Heroic BSoD at the end of Mobile Suit Zeta Gundam as a product of Scirocco's massive Mind Rape, he remains in a vegetative state throughout the sequel, Mobile Suit Gundam ZZ. The few times he's more or less awake, he acts very erratically and occasionally uses his Newtype powers to call out to other characters such as Judau. He successfully recovers at the finale.
Lasse Aeon from Mobile Suit Gundam 00 was healthy in the first season, but in the second one he had quite the Incurable Cough of Death. It's apparently a consequence of his battle with Alejandro Corner.
Shigeo "Mob" Kageyama of Mob Psycho 100 has chronic anemia and frequently passes out from overexertion despite his diligent commitment to the Body Improvement Club. While this is normally played for laughs, it also proves to be a Drama-Preserving Handicap when Toichiro initiates his plan to take over Seasoning City just after Salt Middle School's annual 5 km marathon and Mob, already exhausted and injured from the run, passes out early into Claw's assault.
Michio Yuki from MW. Not only the titular chemical warfare turned him into an asshole beyond redemption, but also gives him occasional headaches, getting hospitalized at one point, and only a few years left to live.
In My Hero Academia, the world's greatest hero All Might is, in secret, barely able to use his powers after a debilitating injury he got fighting one particularly powerful villain, costing him his stomach and half of his respiratory system. He ends up coughing up blood when he overuses his powers, forcing him to use them for only a short while each day, and his true form is highly emaciated as a result of his injury.
His predecessor, the very first One For All user, was also this. What his exact illness was is never said, but he was frail and sickly his entire life. It was made even worse by his older brother's horrible abuse later in life.
Oddly enough, Mai Tokiha's brother Takumi from My-HiME and My-Otome manages to fit this trope while also being a domestic type (at least in the former show), and is inordinately fond of his older sibling.
A villainous example is Kimimaro Kaguya from the Sound Five. It's implied to be tuberculosis or something similar, as he coughs a lot and has a very shortened lifespan.
Likewise Itachi Uchiha, afflicted with an unspecified illness that gives him Blood from the Mouth.
Trafalgar Law was gravely ill for most of his childhood, due to the Amber Lead Syndrome (a illness similar to asbestos that killed Law's family and people due to the World Government's negligence). Law was the Sole Survivor of his homeland and was so broken by it that he became a Creepy Child, whose only wish was to kill as many people as possible before dying. Doquixote Doflamingo took Law in and, in Evil Mentor style, raised him as a killer — but Doflamingo's younger brother Rocinante took pity on Law and traveled all over to find him his cure, despite Law trying to kill him when they met. He succeeded and got Law to eat the Ope-Ope Fruit, which saved his life... but wasn't fast enough to save his own life, and died at the hand of his cruel older brother (who not only wanted the Ope-Ope Fruit for his own gain, but was already pissed off after finding out that Rocinante was The Mole for the Marines). This was terrible for the now healthy Law, who had grown to love Rocinante like an older brother/father-figure, and ultimately gave him his biggest purpose in life: to become a pirate and kill Doflamingo. He and Luffy don't get to kill him — but they do dismantle his evil empire, reveal his deals to the world, and defeat him in a massive fight that ends in him being imprisoned at Impel Down, which may count as a Fate Worse than Death.
Doc Q from the Blackbeard pirates, is always sickly and rides a equally sick horse. Though he seems to be on the verge of death in all his appearances, he's still seems healthy enough to sail a ship and burn islands down.
Phantom Quest Corp.: Bosco is a vampire who's trying to kick the habitnote in order to be with Makiko, a 19-year-old college freshman that he's fallen in love with. So he limits himself to only feeding 4 times a year, at only 200cc's per quarter while taking supplement tablets in between. Which has taken its toll on his health, leaving him anemic and severely weakened. In his brief tussle with Ayaka, he was only able to hold her off for a few seconds, before he exerted himself and fainted.
Zen Takazuchiya, a minor character in Phantom Thief Jeanne, has a heart condition and is possessed by a demon. Maron tries to checkmate the demon but is informed that the demon is what's keeping Zen alive. Maron decides she'll just wait until Zen recovers but Sinbad checkmates the demon instead leading to Zen's death.
A further subversion is that Yukimura does in fact have a specific illness (Guillain-Barré syndrome, a disease of the nervous syndrome) which led to some fan complaints after he recovered, because this condition is incurable. It's later handwaved in an author's note, apparently: he does not suffer from Guillain-Barré, but from a similar illness... which is not mentioned by name.
And his condition is spoofed mercilessly in the Chibi episodes, where he collapses and dies every five seconds much to Sanada's despair. "YUKIMURAAAAAAAAAAA!!!!!", indeed.
Kyousuke Kamijou from Puella Magi Madoka Magica was a talented violinist involved in an accident, thus we meet him in the hospital and see that not only his arm was injured to the point that he won't be able to play anymore, but he must go through painful therapy to regain use of his legs. The manga goes further by directly showing the horrible scars on his arms. Sayaka Miki, Madoka's best friend who fancies Kamijou, becomes a Magical Girl and uses her wish to heal him so he can play again. Unfortunately, Sayaka's motive for healing him was anything but selfless and she is driven to despair when she can't summon up the courage to confess to him, resulting in her becoming a witch soon after Hitomi Shizuki confesses to him instead.
Subverted and parodied mercilessly by the manga-only character of Densuke in Ranma ½. He is a sickly, bedridden boy who muses that he will die by the time the last persimmon falls from the tree outside his window... cue female Ranma coming by with a huge sack to pick all the persimmons herself. Densuke's illness is never specified, however, he is relatively healthy (if abnormally weak) and all it would take to cure him is a single dose of a powdered medicine. He refuses to take it, though, unless delivered mouth-to-mouth by a pretty nurse.
Parodied earlier in both the Manga and the anime by the "ill boy" who insisted on keeping Genma (in his Panda form) as a pet. It turns out he isn't sick, just lazy (and spoiled.)
Romeo's commoner friend Petruccio from Romeo × Juliet, afflicted with what's all but stated to be turberculosis. He dies in Romeo's arms in the same episode he's introduced.
Another adult ill boy is Kenshin's Big Brother Mentor Takasugi Shinsaku, from the Rurouni KenshinTsukiokuhen OAV. Based on the Real Life samurai of the same name, who also was an ill boy. Both were affected with tuberculosis, and RK!Takasugi was almost in the last stages of his illness when he finds and recruits Kenshin into the Ishinshishi group, proved by his nasty and bloody cough. Neither the real nor the fictional Takasugi lived enough to see the beginning of the Meiji restoration.
In the original series we have Kenshin and Saitou's old rival Souji Okita, the most badass member of The Shinsengumi — who also has tuberculosis and is seen coughing his lungs off. Just like Takasugi, he was based on a real life figure affected by such an illness. And again, just like Takasugi and his own RL counterpart, Okita died before the Restoration.
Mikoto Saijou from Saijou no Meii was this, and then was operated on succesfully. Ever since then, he's been working hard to become trhe best child surgeon ever.
Luna's sort-of temporary love interest in the movie (and in a side-story of the manga) was an ill boy scientist named Kakeru Ohzora. The MacGuffin of the movie (a crystal belonging to the Big Bad, Princess Kaguya), which is in his possession, saps his Life Energy away as the movie passes — he starts relatively healthy, then starts to cough and later is weakened and bedridden. He gets better
In the manga story on which the movie was based Kakeru was a legitimate ill boy with heart disease.
Mamoru Chiba spent the last part of the Super S season as an ill boy as the Dead Moon Circus takes over ther Earth more and more, which causes him great physical pain and weakness since, as Prince Endymion, he's the equivalent of Sailor Earth. When the Circus is banished away, he gets better.
Masataka's little brother Mitsugu from Sakura Gari. He was born with a weak heart, barely survived Spanish influenza in the past, and in-series he gets pneumonia. Ouch.
In the original The Secret Garden, Colin Craven isn't ill per se but is weak and gets sick a lot from spending all his time shut up in his room, never leaving his bed and having hysterical tantrums. In the Animated Adaptation, Himitsu no hanazono, Colin still throws tantrums and holes up in his room, but is genuinely sickly. And he is at least once in the verge of death.
Shuu Tsukiyama is revealed to have become one in the sequel Tokyo Ghoul :Re. Two years of grief and starvation over Kaneki have left him bed-ridden, with his physical condition so poor that he has lost his sense of smell. A pair of long-time companions have been attempting to improve his health, though oppose each other on what will actually kick start his recovery, and one of them (Kanae) is willing to go the murderous way.
Played with in UFO Robo Grendizer. Duke Fleed/Daisuke Umon is an Ill Boy who's actually dying of radiation poisoning... and the lead character
Minato from Wish Upon the Pleiades is one. This is the driving motivation behind his actions as Dark Star/Horned Cape.
Mixed Examples
In Akatsuki no Aria, both Shiroyuki-sensei and his wife Kimie turn out to be seriously ill. In her case, she already was in the last stages of tuberculosis and died alone in a sanatory, which is VERY messy since her family mistakenly thinks Shiroyuki was fooling around with Aria when she was dying (In reality, he was helping her out with her hand injury). In his case, he was diagnosed with tuberculosis almost immediately after being widowed; he believes it's his punishment for having neglected Kimie, and he dies few later too.
In Gangsta., the entire Twilight race is essentially compromised of these. All of them are born addicted to a Psycho Serum that they must take daily to prevent the withdrawal symptoms — only for the drug to eventually accumulate in their systems, breaking down their bodies and killing them. The whole reason they're called Twilights is because the this effect makes it a damn miracle if any of them live to hit thirty.
This is quite literally the name of the story, Ill Boy, Ill Girl. The disease in question has them die on their 12th birthday and both the male and female leads are afflicted by it.
, which only appears in women since it's associated to X chromosomes. It made her look extremely different from her long-separated, half-identical twin brother Raita Banba... who unfortunately turns out to be the guy she was going to marry. Alongside several other factors, this totally broke poor Hatsune's heart and mind once she found out, and she ultimately was Driven to Suicide. And for even worse, Raita was mistakenly accused of killing her, and Conan/Kogoro had to work hard to get him free.