Kid Heroes in anime and manga.
- Astro from Astro Boy is the Ur-Example in manga. He's a Robot Kid who is socially and mentally a little boy (having been created to resemble a dead 8-year-old boy), and is constantly saving people.
- Asta, Yuno, and Noelle from Black Clover are the Main Characters of the story and the youngest members of their squads due to recently receiving a grimoire at the age of 15 in the beginning of the story.
- Summed up in one line from Bleach; when Chad is offered the chance to end the battle and drink with Shunsui Kyōraku, he refuses. When asked why, he points out, "It's illegal for minors to drink;" it's quite easy to mistake Chad for an adult. Along with Chad, Ichigo, Orihime, and Ishida are all 15. (17 now.) The shinigami most associated with them are Rukia and Renji who are biologically-speaking age-group peers of them, and Hitsugaya who, despite being a captain, is actually biologically younger than them all (around 13-14).
- Blue Exorcist: Rin Okumura is an Anti-Anti-Christ version of this trope.
- The Bokurano kids thought they would become this. They were wrong. Played most obviously with Waku: he comes off as a stereotypical, boisterous Hot-Blooded shonen Kid Hero who is gleeful to ride the Humongous Mecha... And he is the first to die, not even making it to the end of the first manga volume, and serves as the Decoy Protagonist.
- The shows in the Brave Series are technically this, except in The Brave Fighter of Sun Fighbird, GaoGaiGar and the OVA sequel GaoGaiGar FINAL, where the heroes are an Android, a Cyborg and an Evoluder, respectively.
- One of the main characters of GaoGaiGar, Mamoru Amami, is a rather interesting example of a normal boy who develops into one over the course of a series. Originally an ordinary grade school student, Mamoru becomes the Tag Along Kid to the heroes of the Gutsy Geoid Guard because he's the only one who can purify Zonder cores and turn them back into humans. Apart from flight and a rather potent shield which he can't consciously manifest (at first), he has no combat ability whatsoever, and his first attempt at purifying a Zonder on his own nearly gets him killed. At some point, however, the sheer awesomeness of his coworkers began to rub off on the little guy, and by the end of the TV series he'd achieved a lot despite still not having any real combat ability, and goes up against Humongous Mecha-sized opponents on more than one occasion without getting squished. Then FINAL rolls around, and Mamoru comes back after a extended absence on Earth with several shiny new Levels In Badass; his healing powers have developed into a full-blown Holy Hand Grenade, his shield is capable of tanking direct hits from mecha-scale energy weapons, and he gets a Final Battle with his very own Evil Counterpart. And just to put the cherry on the kid's Awesome Cake, Mamoru's courage and refusal to surrender single-handedly tips the scales of the Final Battle by powering up the G-Stones of all of 3G's giant robots, giving them the energy for a chain of My Name Is Inigo Montoya moments. Not bad at all for an 8-year-old.
- The planned though sadly cancelled crossover between Betterman and GaoGaiGar would have had him finally promoted to piloting a mecha along with Kaidou.
- One of the main characters of GaoGaiGar, Mamoru Amami, is a rather interesting example of a normal boy who develops into one over the course of a series. Originally an ordinary grade school student, Mamoru becomes the Tag Along Kid to the heroes of the Gutsy Geoid Guard because he's the only one who can purify Zonder cores and turn them back into humans. Apart from flight and a rather potent shield which he can't consciously manifest (at first), he has no combat ability whatsoever, and his first attempt at purifying a Zonder on his own nearly gets him killed. At some point, however, the sheer awesomeness of his coworkers began to rub off on the little guy, and by the end of the TV series he'd achieved a lot despite still not having any real combat ability, and goes up against Humongous Mecha-sized opponents on more than one occasion without getting squished. Then FINAL rolls around, and Mamoru comes back after a extended absence on Earth with several shiny new Levels In Badass; his healing powers have developed into a full-blown Holy Hand Grenade, his shield is capable of tanking direct hits from mecha-scale energy weapons, and he gets a Final Battle with his very own Evil Counterpart. And just to put the cherry on the kid's Awesome Cake, Mamoru's courage and refusal to surrender single-handedly tips the scales of the Final Battle by powering up the G-Stones of all of 3G's giant robots, giving them the energy for a chain of My Name Is Inigo Montoya moments. Not bad at all for an 8-year-old.
- Hyoma Aoi and his group from Combattler V were all teenagers.
- Allen Walker from D.Gray-Man is 15 at the start of the series and perhaps 16 in the latest chapters. He still goes through more crap than most adults.
- Daicon III stars a young girl who is entrusted with delivering a glass of water, single-handedly fending off the many threats that dog her on the way.
- Kazuya Ryuuzaki from Daimos has been astronauting since he was 14. His Disappeared Dad and his Parental Substitute were scientists.
- Every protagonist of all Digimon series, both anime and manga, except Digimon Data Squad (and even it still has a few).
- Dragon Ball:
- Goku for most of Dragon Ball. Child Goku was so popular in Japan, that they tried to bring him back for Dragon Ball GT by having him wished into a child with the Dragon Balls.
- In Dragon Ball Z, the role was filled by Gohan, and after the Cell saga, Trunks and Goten. All three are deconstructions. Gohan was put through Training from Hell shortly after being kidnapped by his father's archenemy, at the age of four. During his first battle a year later, he spends some vital moments paralyzed with fear. After losing her husband and her son for a year, Gohan's mother forbids him from fighting (even though he always has to). Goten and Trunks take the opposite route. While they are much more powerful than Gohan was at their age (7 and 8 respectively), they treat fighting like a game. As Gotenks, they aim for Showy Invincible Hero and act out anime tropes like Heroic Second Wind just because it's cool. When fighting against Majin Buu, their desire to show off and prolong the fight results in them missing chances to deal the finishing blow, and even accidentally traps them in an alternate dimension.
- Renton Thurston from Eureka Seven. Mind you that this character is voiced by Johnny Yong Bosch instead of Yuri Lowenthal in the English dub (he was originally though).
- Edward and Alphonse Elric from Fullmetal Alchemist. Edward joined the military at the age of 12, and during the events of the series, he's 15 (turns 16 at some point). Alphonse is one year younger.
- Fushigi Yuugi and its prequels have some cases:
- The Priestesses tend to be junior high/early highschool students. Miaka and Yui are seen fretting over their highschool admission exams in the original, while Takiko's first appearance in Genbu Kaiden shows her at school (more exactly, at naginatajutsu practice). Suzuno turns out to be the youngest one of them all, entering the World of the Four Gods for the first time when she's 8-years-old since her father sent her there to protect her from the Great Kanto Earthquake. While she gets out of there soon, near all the Byakko-related artwork shows her as a young girl no older than 14/15...
- Some of the Senshi are also in the child/pre-teen/teenager age range, with Hatsui from Genbu Kaiden and Chiriko from the original as the two youngest — at the age of 12-13.
- Hayato Kazami from Future GPX Cyber Formula is a youngster who just entered Cyber Formula racing at the start of the TV series and in the end he won the championship, all at the age of 14. He ages throughout the series, and by the time of SIN, he reaches adult age and is 21-years-old.
- Ryoma, Hayato, Musashi, Benkei and Michiru from Getter Robo were high-school students when the series began.
- Gin in Ginga: Nagareboshi Gin. While Gin becomes a Living Legend in Ginga Densetsu Weed, his son Weed takes over this role.
- Takeru Myojin/Mars from God Mars is stated to be 17-years-old.
- 15-year-old Garrod Ran, an ex Street Urchin, becomes the pilot of the titular Gundam X Real Robot, with his also 15-year-old love interest Tiffa Addil following him in his adventures. His Team Dad and mentor as well as Tiffa's adoptive father, Jamil Neate, used to be one as well... but he actually had a complete breakdown after the war, which didn't let him pilot a mecha in more than 15 years.
- This holds true for most Gundam series. The only ones who are never underage are Kou Uraki, Domon Kasshu, and Shiro Amada.
- Hello Sandybelle: Sandybell is 12 at the start of the story. She helps bust corrupt drug dealers, saves animals from danger and rescued Edward while he was drowning, amongst other deeds. Her heroism is rewarded when rescuing a drowning orphan set off the chain of events that caused her amnesiac long lost mother to regain her memory/
- Joey Jones from Heroman, more appropriately, The Kid with the Remote Control.
- In Hiwou War Chronicles, the protagonist and his group of siblings and friends are all children who journey across Japan in a clockwork giant mech named Homura. Jyoubu, the baby in the group, even has a role in activating Homura — he's left swinging around as a counterweight in a bowl.
- Hunter × Hunter has Gon Freecss and Killua Zoldyck, both of them were twelve when the series started. It's a deconstructed trope; on the one side, Killua was tortured with poison and electro shocks since his birth due to his family assassin training, resulting he has become immune against them. When he is about to kill or threat someone, his personality becomes pretty cold and dark. On the other side, Gon started as a Goku Expy, but when the series progress, he has become more aggressive and deadly, even taking a innocent hostage to force his enemy to heal his mentor, only to learn that his mentor was already dead. This triggers Gon's ultimate Nen and he forces himself to grow up into an adult, so that he can finally kill his enemy.
- Jojos Bizarre Adventure: Due to their mature appearances, it's easy to forget that some of the JoJos are still in high school during their respective parts. The most impressive example would be 15-year-old Giorno Giovanna, who ends up becoming Boss of Passione by the end of Vento Aureo.
- Special mention goes to 11-year-old Emporio Alniño, who is the one to ultimately defeat the Big Bad of his respective part, Enrico Pucci
- Kimba from Kimba the White Lion combines this trope with A Child Shall Lead Them.
- Kirby: Right Back at Ya!: Kirby in the games has a Vague Age, though he's implied to be fairly young. Here, he is explicitly a baby, yet still fairly capable against every Monster of the Week.
- Hiroshi Shiba from Kotetsu Jeeg was also underage. And an amateur car racer. And Cyborg capable transforming into the head of a Humongous Mecha. And he looked after his mother and little sister after his father's murder.
- Kouji Kabuto from Mazinger Z was sixteen when began the series. His Battle Couple, Action Girl Sayaka Yumi and their friend Boss were the same age, and his brother Shiro was roughly 10-years-old. Tetsuya Tsurugi and Jun Hono from Great Mazinger were slightly older (although you would be hard-pressed to tell with Tetsuya, since he might be quite immature sometimes). It is hard to tell if Duke Fleed from UFO Robo Grendizer was underage or not, but Hikaru Makiba and his sister Maria were still teenagers.
- While several of Miyazaki's films feature kids or teens as protagonists, Pazu and Sheeta from Castle in the Sky arguably come off as the most heroic. Though Kiki from Kiki's Delivery Service has her moment, too.
- Magical Girl Lyrical Nanoha: Nanoha Takamachi who became an adult over the course of the series. She started her "career" at the age of nine and later is in command of several teen heroes.
- In Monster Rancher, Genki is an eleven years old grade schooler who carries teenage girls around like other kids their satchel. His very first fight starts with him kicking a genetically modified velociraptor in the face. And not a little kick either, hell no. He is portrayed as being an uber, uber, powerful chosen-one who can do things nobody else can even the monsters, however.
- In My Hero Academia, the students of U.A. are 15 when they begin attending to become licensed superheroes and the protagonist, Izuku Midoriya, is introduced as a 14-year-old in his last year of middle school.
- Naruto:
- In Naruto, the main characters start around 12, in part II they're 15 and by the end (excluding the Distant Finale) Naruto's age is 17. They're all ninja but the series usually shys away from portraying them as outright Child Soldiers.
- In Boruto, Boruto and his friends start off as ninja academy students. Their exact ages aren't mentioned but they're clearly between 10 and 12.
- Negima! Magister Negi Magi: Nagi Springfield during his youth certainly qualifies. At age 10, he wins the Mahora Tournament, and could fly without a staff and essentially teleport. Gathering a team of badasses and becoming a war hero, he receives the title of Thousand Master at age fifteen. His son and series protagonist, 10-year-old Negi aims to be just like him - he's already led his side to victory in the Battle of Mahora "game", and was able to go toe-to-toe with one of his father's contemporaries in an all-out fight.
- Deconstructed in Neon Genesis Evangelion. 14-year-old Shinji has a complete breakdown under the pressure of being the designated hero, whereas Asuka suffers a similar breakdown and Rei suicides all over the place. And Touji either gets mauled and crippled or dies, depending on which continuity you go. One of the episodes is even titled "And he was aware he was just a child". Indeed, one of the Central Theme of this anime is that the idea of putting the entire world's safety on a bunch of kids' shoulders is suicidally stupid and impratical in Real Life.
- Hattori and Kenichi of Ninja Hattori are both child protagonists.
- Nurse Angel Ririka SOS: Multiple:
- On her tenth birthday Ririka receives a gift from the mystery New Transfer Student which allows her to become the Magical Girl "Nurse Angel". Her friend Seiya eventually begins tagging along as well.
- There is a legend on Queen Earth that specifically states a 10-year-old girl called "Nurse Angel" will protect the universe in times of crisis. Ririka is a reincarnation of Nurse Angel.
- Luffy from One Piece barely counts at age 17, but many people look at him as younger. Word of God wants to reinforce that minors still shouldn't drink. He's still treated as one after the Time Skip, even though he's now 19.
- Panzer World Galient: Jordy Volder, Crown Prince of Arst, swordsman, Humongous Mecha pilot is a 12-year-old kid and this story's hero (not that the circumstances give him much of a choice in the matter).
- In the Pokémon universe you're allowed to become a trainer at age 10, or younger in the games. Ash Ketchum Jumped at the Call at this age. Most heroes, including the ones from Adventures and the original games start at 10 to 12. Still, people don't have to become trainers then; it is possible to become a trainer later, as demonstrated in Pokémon Black and White. However, it is worth noting that since Comic-Book Time is not in effect in Adventures, the first gen heroes are now in their twenties.
- The whole theme of the Pretty Cure franchise is a group of teenagers saving the world from evil. The ages of the protagonists range from 10 to 17, with the average age being 14.
- Akira Hibiki from Raideen was a high-school student.
- Haru Glory from Rave Master (no surprise who voices this character in the English dub).
- Tsuna Sawada from Reborn! (2004) is around 14-15, and so are most of his guardians. Special mention to Lambo, who's 5.
- In Rebuild World, Akira is a young teenager fighting to survive in the slums with no one to guide him until he encounters Alpha. While he's far from "good", he doesn't like having unpaid debts and shows genuine gratitude to those who help him out out of the kindness of their hearts. In addition, the story emphasizes just how naïve and inexperienced he is because of his age. He would be dead dozens of times over if not for Alpha, who leads him by the nose to get what she wants.
- Sailor Moon:
- Almost all of the Solar Sailor Soldiers at the very least start out as "hero kids". The Inner Scouts are this most especially, all of them school-aged girls in their teens. However, this becomes brutally deconstructed in the first season finale — Usagi witnesses their closest friends get killed one by one and is naturally not well-equipped to deal with it.
- The exception being Setsuna Meioh AKA Sailor Pluto, who is already in her twenties when she appears.
- Sailor Uranus (Haruka Tenoh) and Sailor Neptune (Michiru Kaioh) technically start out in this group, being 16-17 when they appear, but both live like adults by the 5th season (not going to school, living on their own, and co-adopting Hotaru Tomoe along with Setsuna.
- The most extreme examples are Chibi-Usa, AKA Sailor Chibi Moon, who in the Anime version ranges from the age of 6 to about 8, Hotaru Tomoe, AKA Sailor Saturn, who starts out as 12 but after she is killed in Season S is reborn as a baby and ranges from physically being an infant to about the size and stature of an 8-year-old, and Chibi-Chibi, who's only 2- or 3-years-old and can't even talk in complete sentences yet.
- While at first sight this might not be the case considering the authors' tendency of drawing his characters looking way older than they actually are, in Saint Seiya, the five main characters are merely 13- to 15-year-old teenagers. And they have to protect earth from many Jerkass Gods who want to destroy it.
- In Shōnen Onmyōji Masahiro, the grandson of Abe no Seimei, defeats hordes of demons from China, patrols the Japanese imperial capital for evil demons at night, and prevents the world from being over run by the armies of hell at the ripe young age of thirteen.
- The student meisters and Weapons in Soul Eater are mostly around the age of 13, which is either stated or can be deduced from various comments and flashbacks. Those who are noticeably older are the Thompsons (Liz, at least) and Tsubaki. Thunder and Fire are by far the youngest Weapons, or at least it appeared so until they are briefly 'aged' via a power-up. There may have been some sort of timeskip following the Baba Yaga arc, but the art evolution and absence of a clear timeline make it difficult to tell.
- Simon from Tengen Toppa Gurren Lagann, like Shinji, starts out as a cowardly boy; however, since his mentor is Kamina the Determinator, instead of Gendou the cold-hearted, Magnificent Bastard, Simon later becomes a badass Kid Hero.
- Kenichi Go and his team — two of which were his brothers — from Voltes V were also underage.
- In Yo-Kai Watch: Wakuwaku Nyanderful Days, Katie is a fifth grader who befriends various yokai and goes on adventures with them.
- The Hero Club in Yuki Yuna is a Hero is made up of four (later five and then later six) middle school girls who volunteer around town. Unknown to most of them, they have to become Magical Girl Warriors and save the world. It's later revealed they're more like Child Soldiers than normal Kid Heroes, since they're chosen by the government to protect their land from monsters.
- Yusuke Urameshi from YuYu Hakusho, is 14 throughout most of the series. Kuwabara is around the same age.
- Deconstructed with Zambot3. The three main characters are pre-teenagers were pushed by their families to pilot a Humongous Mecha and fight a genocidal psychopath intended to wipe all humans off Earth. At the same time they were hated by the people they were intending protecting. Needless to say, they were through serious breakdowns, emotional abuse and several of them died before the survivor got a final mind-screw. This series went to extreme lengths to show children should not be used like soldiers, depicting infant abuse in a way unparalleled until then.
- On the other hand, Daitarn3, a Lighter and Softer Spiritual Sequel to Zambot3, played it straight. Banjo Haran was a Hot-Blooded, 16-years-old James Bond spy with a Humongous Mecha lived on a manor and was surrounded by beautiful women.
- Jin, Kouji and Asuka in Zettai Muteki Raijin-Oh, there are also Kenichi, Hiromi, and Shinobu in Nekketsu Saikyo Go Saurer; in fact, pretty much every main character in the Eldoran series apply, since all of them are 5th or 6th grader elementary students.
