In Assassination Classroom, the two young boys at the nursery act unusually mature for their age.
First Boy: The action looks so real. Second Boy: Yeah...it's much more stimulating than the Disney monopolized Hollywood.
The main peripheral character, Nagisa Shiota, counts as well. He can read people like a book, is always thinking ahead, sometimes acts as the class’s Only Sane Man, and tends to go on introspective musings that border on philosophical. He’s able to give good enough advice that his words successfully convince a party boy to not only stop smoking, but to use his talents for good purposes, and he also becomes something of a mentor figure for Sakura, so much so that he’s able to get her to go back to school and improve her grades.
Chiyo-chan from Azumanga Daioh can not only handle high school-level schoolwork, she also manages to be a class rep and hold down a part-time job, and is generally just as mature and capable as her teenaged friends. She's ten years old.
Louis invokes this trope when he interacts with others, especially in the first half of the series. He puts on an aura of maturity because everyone expects him to be a larger-than-life figure who everyone should aspire to imitate. But sometimes his facade cracks and he can't help but act like an 18-19 year old, something his surrogate older brothers in the Shishigumi note is "part of his charm".
Haru is more mature than the average third year student especially in regards to relationships and intimacy. It's noteworthy that she's the first person to see right through the aforementioned Louis' persona and realize just how lonely he feels. As Juno puts it.
"Why is this bunny so mature? [...] She talks like a grown-up, but sounds like a child."
It's hard to remember how young the children and teenagers are in this manga. Ichigo, Sado, Orihime and Uryuu start off as fifteen year olds, but are far more mature than their age would indicate. Some of their classmates are the same, such as Tatsuki. Their Shinigami peers are the same: Renji, Rukia, Kira, Hinamori, Ganju, etc., are all teens but behave like adults.
Hitsugaya is (biologically) only 12-13 years old but doesn't behave like a typical child his age due to having been thrust into the role of youngest captain in history. Aizen works out that the truth is obscured and that Hitsugaya does actually have the in-built weaknesses associated with his biological youth (such as lacking both the life experience and emotional maturity of a grown adult). When Aizen triggers this weakness, the ignition of Hitsugaya's emotions into an Unstoppable Rage (and the other captains' inability to have foreseen this weakness) spells disaster for everyone.
Several of the Bokurano kids like Kirie, Moji and Kodama. But 10-year-old Kana takes it to borderline ridiculous levels. Accepting a constant abuse of her older brother Jun and preventing people around them from interfere, because she knows he's angry at their dead mother for her absence, and by taking it out to her he's in reality treating her as somewhat of the mother figure? Not even being Jun's blood-sister, but hiding it from him in order to make him feel secure, she devotes herself to finding his real mother. In the manga, while she's about to die it remains her biggest concern — because Jun's gonna need support after she's gone.
Tomoyo from Cardcaptor Sakura is not only Genre Savvy, but is able to see the hidden intentions of every character she comes across even though she's a fourth-grader.
Even Eriol acknowledges Tomoyo's savviness.
Five year old Hatoko from Angelic Layer dispenses wisdom like Yoda but without the fractured syntax.
CLAMP School has the six year old kindergarten class president, and an adolescent Man Of Twenty Faces who steals large statues from under the noses of the police etc, and more.
Tsubasa Syaoran Li in Tsubasa -RESERVoir CHRoNiCLE- is only seven years old when he first went to Clow Country and met Sakura but somehow, he understands the concept of love, magic, and even deals with the sorcerers. He might as well be the most mature characters in the the series, even more than an adult like Fai or Kurogane.
Kaguya Sumeragi, a fourteen-year-old girl with Puppy-Dog Eyes and a Precocious Crush on Zero, who often turns out to be one of the wisest, reasonable characters on the show and the one person Zero treats with complete respect while callously ordering around the rest of the Black Knights.
Nunnally seems to be in her way to become one of these in R2. After the end of the series, She rules Britannia, Tianzi Lihua, who's even younger than her, rules China, and Kaguya leads the UFN, with an unnamed girl around their age ruling (presumably) Europe (as seen in the Miracle Birthday OVA). So all of the world leaders are cute examples of this.
Don't forget; Lelouch is only 17 when the series begins. Older than most of the examples on this page, but still a little young for the kind of crazy stuffhe pulls off. On top of that, he was already a Chessmaster in his early Britannia days.
In Demon Slayer: Kimetsu no Yaiba, Kagaya Ubuyashiki is a man of deep wisdom, far more than befits his age of only twenty three. He's seen as far wiser and more mature than men many years his senior. The most notable thing is the fact Kagaya managed to make Himejima, who’s 4 years older, consider him, the younger person, to be his father figure.
The human cast of Digimon Tamers exhibited a maturity way beyond their 10 to 11 years, one of several possible reasons their ages were raised in the English adaptations.
Every season of Digimon has one of these… even Digimon Frontier's Bokomon, who is the level named "child" in Japanese and who speaks and acts like a graduate student specializing in Digital World Mythology.
Henry/Jian of "Tamers" takes the cake though. It is stated above he's 10-11 in the Japanese version, yet he can hack almost any computer system if you give him a good reason, and uses the word incorrigible in a relatively casual conversation.
Mikey, Nene, and Christopher from Digimon Fusion act more mature than most adults, and they're only 13.
Sora and Joe are the most mature of the original cast of Digimon Adventure, and as such take up the roles of Team Mom and Team Dad respectively while Tai and Matt fight over leadership, thinking of responsible things like how they will get food, what best course of action to take, and how to keep the group together. Tai later matures up later in the season as well.
Child Lucy in Elfen Lied. Unfortunately, her childhood was traumatic enough to the point that she turned Ax-Crazy.
Most of FLCL revolves around how Naota rejects his childhood.
Alphonse Elric. While his older brother, Edward, wins critical acclaim time and time again for accomplishments thought ridiculous, Al consistently proves that he is rational, fair-minded and far-sighted far beyond his years. In fact, he often has to reign in Edward to prevent excess damage and often has to clean up if he's not able to prevent such excesses.
Edward himself proves to also be very wise and have a great understanding of the world, which in the end allowed him to recover his brother Alphonse by sacrificing his alchemy. The series put much emphasis in the growth and maturing of the Elric brothers and the characters in general. When we finally meet Ed and Al's alchemy master Izumi Curtis she comments how wise Edward must be to be able to perform alchemy without a circle however Ed responds that he isn't wise or clever; he just learned things he shouldn't have done by opening the gates of truth
In most cases Ling Yao is a perfectly good example of this serving. He keeps a cool head and is slow to anger and he notices things that others don't.
Tessa from Full Metal Panic! is only 16, yet she is the captain of a submarine. She also shows a great understanding of people and exhibits a very mature attitude. She's also damn good at her job. However, she is not completely immune from some general characteristics of teens.
Sōsuke is 16-17, and is a sergeant within a paramilitary counter-terrorist force. Although extremely immature for his age about relationships and social skills, he is shown to act very professional and understanding about things involving war. He was trained to be a professional assassin at age 8, and became a terrorist at 11.
Weed of Ginga Densetsu Weed is supposed to be this trope, though to most of the audience he comes across as being overly nice to the point where he makes bad decisions like letting other dogs that tried to kill him live. Imagine if during any real war, one side let ALL enemies soldiers go after they tried to kill their troops or worse leaders and it readily becomes apparent how stupid Weed's decisions are. It's sending them back to their army to kill again.
Well to be fair, in the manga, it was two random spies that Weed wanted to be merciful to after the spies begged for their lives. These dogs did not actively try to kill Weed or his comrades. The anime for some reason replaced the spies with the assassins Thunder and Lector. Also in the manga, it is directly shown that Gin had always agreed with Weed's stance on killing, and him seemingly trying to kill Hougen was actually a test to see if Weed was a true leader. In the anime, it is the same way but it's not as clearly explained. It's also worth noting that Gin let Sniper live in GNG even though the doberman tried to kill him and his comrades multiple times.
13-14-year-old Victorique de Blois from Gosick, though she admittedly has traits common for a child of her age, such as curiosity and a love for sweets.
All the girls in Gunslinger Girl are aware that they are on borrowed time, and that their feelings for their handlers are at least partially the result of conditioning. Triela and Claes are the only two to have made their peace with the fact they will never see adulthood. Though they deal with the knowledge in opposite ways (despite being roommates).
Wendy Garret of GUN×SWORD, who's maybe 13-14, is in many ways more mature than her traveling companion, Van. More importantly, she functions as the moral center for the series, being one of the few characters to think deeply about the moral/ethical issues surrounding The Claw's plan.
Hanaukyō Maid Team. Grace is considerably more intelligent and wiser than the other maids, even though she's younger than they are.
Both Kyon and Koizumi of Haruhi Suzumiya fit. Kyon is a little too much of a jaded cynic for just being 16-years-old.
Fuji-hime from Harukanaru Toki no Naka de might fit this trope, since she is effectively the team's mentor — even if most of her knowledge comes from her ability to see the future, she is arguably more mature than some of the members of the central cast (whose age ranges from 14 to 32, with Fuji being only ten). Might have something to do with her destiny to assist the main character, but still...
17-year-old Maria from Hayate the Combat Butler already has a full-time job as a maid, and is also mistaken for being in her late twenties or early thirties because of her maturity level.
Maria is continually pointed out to be not mature, but intelligent.
Hayate himself, almost certainly... he's a full sixteen now, but has already evaded the yakuza, served under Athena (who is supposed to be of similar age), and is already a prize-winning manga artist… seriously, with the luck factors so hard down his throat, he really had to be to make it past the age of 8…
Hayate clearly states that he supported his parents starting at 10. His bad luck is more of an informed ability than anything given that he is the main male in a harem story.
Though one could argue that that is bad luck considering the amount of physical and mental abuse he suffers because of it. Especially bad luck considering he is surrounded by a harem and yet is forced to be a Chaste Hero until he has enough money to support even one of the girls, which, given his 150 million yen debt, is highly unlikely.
Hinagiku also has a similar level of maturity, most of the major cast in on the low end of this trope as well, showing maturity beyond what someone would expect from a 16/13 year-old. Even Yukiji seems to have it, when it's not overshadowed by her Hard-Drinking Party Girl tendencies.
Anna Kushina of K, particularly in Season 2 after she Awakens as the new Red King. Probably due to her empathic powers — if she's able to understand all sides to an argument, that gives her the experience to understand all different sorts of people enough to be truly wise, even at age 11.
Murasaki in Kure-nai yo-yos between believably childish behavior for her age of 7 and extremely adult-like decision-making, especially near the ending of the series.
The first time we see the 9-year-old heroine Nanoha she's pondering the direction and purpose of her life. Later, when she discovers her powers, she almost immediately takes a responsible view of them akin to Spider-Man, except her wakeup call was property damage rather than the death of a loved one. Her parents also don't seem to mind their daughter taking time off from school to chase after magical artifacts.
The series also introduces us to Hayate. A wheelchair-bound 9-year-old who takes care of the Wolkenritter as their mother figure. Even before then, she had been living independently for who knows how long after her parents died. You'd expect that her guardian would at least have an adult look after her, especially considering her disability. In any event, it's highly unlikely that any social service would let this one slide.
Interestingly enough, Hayate, looking back on her childhood in Sound Stage M4, laments that she feels as though she hasn't grown up since then. Signum then responds that she has grown up at a reasonable pace, and that by comparison, Fate grew up too quickly.
Several other characters are like this as well, especially the calm and mature (if originally single-minded) Dark Magical Girl Fate, Adventurer Archaeologist Yuuno and interdimensional cop Chrono (who actually starts off under the command of his own mother in a sort of pseudo-subversion). One can assume that either Midchilda does not have the same cultural or legal expectations about Age of Majority that most Earth cultures do, or very clear laws allowing exceptions.
The only real aversion is Vivio, who actually acts like the 6-year-old she's supposed to be. Although this only applied when she was 6. By the time she hits 10, she's just as mature as everyone else.
Shiro Kabuto from Mazinger Z and Great Mazinger seems pretty mature for his age (specially compared with Kouji), and actually he is smarter than he looks. This is because Shiro is a full-fledged Iron Woobie is forced to life on his own withou a parents' care. His parents were dead, it is implied his grandfather Juzo spent most of his time building Mazinger-Z, and Kouji is busy handling the household jobs and going to school, thus leaving him alone. And let's not forget his supposedly dead father was too busy building Great Mazinger to take care of them AND tell them he was alive.
Haman Khan from Mobile Suit Zeta Gundam is this trope, being the cool, mature Neo-Zeon commander at the age of 20-21. While this is in part due to her competence and Newtype capabilities, it's also justified due to having been made the de facto leader of Axis as a young teen, forcing her to grow up far quicker. While works like Char's Deleted Affair further show her transformation from optimistic wide-eyed girl to embittered if chillingly dangerous woman.
Lacus Clyne in Mobile Suit Gundam SEED inherits control over a large anti-war faction in ZAFT from her father at the tender age of 16, and immediately engages in skillful political maneuvering and alliance-building surprising pretty much everyone who saw her as just another gentle pop-singer. While doing all that, she also somehow finds the time to play the therapist for both of the series' male leads, Kira and Athrun, and eventually brings both (and their mechs) under her banner, which serves to boost her faction's firepower considerably.
Shikamaru, though you may pass him off as just a Teen Genius but he also already has plans for the future including his marriage, how many kids he wants and when he'll die. Not to mention he was willing to have both himself and his best friends go up against a much stronger opponent that would most likely kill them as to further the mission. This is all when he's 12/13. As Child Soldiers most of the cast would qualify but Shikamaru is the best example.
Itachi and Kakashi's backgrounds cast them as even more extreme cases: Itachi graduated the academy top of the class at 7 (all of the main cast did that at 12), passed the chuunin exams at 10, and became an ANBU captain at 13. He joined Akatsuki at 14 or 15. Kakashi graduated at five, passed the chuunin exam one year later, and became a jonin under special condition at 13.
Another good example is Sasuke, who was designed specifically to be in this trope as a contrast to Naruto. The author even revealed that he had trouble drawing him at first because he had a lack of experience in drawing characters who are "wise beyond their years".
A far more convincing example would be Gaara post-Heel–Face Turn: after years of serving as Sunagakure's Fifth Kazekage, he has not only become far more intuitive and rational compared to his hot-headed equals from other villages, he is also far more compassionate even to a now-Ax-Crazy Sasuke and a troubled Naruto.
Gaara: Peace under an illusion is not true peace. Peace is only meaningful when the world manages to accomplish it.
HinataHyuga is the only one who sees Naruto for who he truly is long before any of the other characters do. She offers him assurance and gives him back his confidence as Naruto fights Neji. Before that, though, she sees and understands Neji for the troubled and suffering soul he really is, which really set him off.
Almost all the child characters count to varying degrees, at least when compared to real kids their age. Justified that they live in a society where kids are given huge responsibilities from an early age, even being able to become ninja.
While 10-year-old Negi of Negima! Magister Negi Magi still very much enjoys being a kid, he has dedicated months of time to brutal Training from Hell, shown a deep understanding of both his friends and enemies, and has a powerful drive to find his father, such that he is willing to make great personal sacrifices. This on top of being a high school teacher of a Wacky Homeroom.
This gets covered in lampshades during second half of the Mahora festival arc, where just about everybody states that Negi is too young to be thinking about the moral implications of protecting the The Masquerade. Later on, he gets all sorts of speeches about how he should just act like a normal kid and stop worrying about everything. None of them penetrates his thick skull.
Negi is a Deconstruction of this trope as he literally has no idea how to be a child. Once when he was on vacation and was supposed to just have fun he tried approaching it the same way he does everything else: by carefully analyzing the situation and coming up with most efficient solution, until Asuna told him he should just relax for once.
There's also Yue. Fourteen-year-old high school student versed in philosophy and Negi's sounding board for moral dilemmas.
Chisame also qualifies, as she arguably has the best grip on reality out of everyone, and Jack Rakan even identifies her as being the advisor that Negi benefits most from.
Satsuki Yotsuba is head cook of a roadside cantina that she established with her fellow classmates. At the age of 14, she already has her future planed and is actively working to achive it. Even Evangeline respects her.
Asuka is a 14-year-old Teen Genius and something of a special case. On one level she understands just how suicidally dangerous being a pilot is, and has made peace with it (at least at first). She also shows impressive understanding of other people's motivations and relations (with the notable exception of Rei — she's aware of Misato/Kaji, just in denial). On the flip side, she is very short-tempered and bratty.
There's also Rei, who is cited by another character as seeming "far older" than the rest of them.
Doremi's sister Pop in Ojamajo Doremi, so much that her parents let her go on a train trip by herself. She's five years old at the time. Although it's clear at least that their mom Haruka was worried, as she asked Doremi to keep an eye on her after Pop had gone.
Almost every single one of the Pokedex Holders/Owners in Pokémon Adventures. With little exception, some more than others; a vast majority of them from the first four generations act like teenagers, if not older, including Idiot Hero Gold, despite the average age being eleven (and in Sapphire's case, ten), with some of them even thinking of their future careers already. This is especially noticeable with Blue (especially jarring since his game counterpart could easily qualify as a Bratty Half-Pint if the player wasn't the same age as him), Green and Silver, though Green and Silver have the excuse of a Dark and Troubled Past explaining their Troubling Unchildlike Behavior, with the only exceptions being Diamond, Red (at least initially) and maybe Sapphire, Emerald, and Sun but even they have their moments. Ironically in the case of Black in the fifth generation, his initial characterization arguably actually made him act like how someone the age of previous Dex Holders should have (though even then the Dex Holders of the fifth generation save for Black had the distinction of actually having jobs, one of them even being self-employed and another being an International police officer). Then the X and Y arc showed that X actually was a full-time professional battler as a child, and the Sun and Moon arc has Sun in millions of dollars in debt and Moon as an established pharmacist; it's heavily implied this is normal for the manga universe, however, if the fact that no one seems to think this is strange is any indication.
Every single member of the Arcobaleno in Reborn! (2004) qualifies. Reborn himself could be a serious contender for poster boy of the trope, even before we knew the other six. Actually an Averted Trope as it turns out that they're all adult assassins cursed with the appearance of infants.
Sailor Moon: Ami Mizuno (Sailor Mercury) is only 14-years-old, yet is the most mature of the Senshi and always cares about studying even when she doesn't need to. Being a Shrinking Violet who becomes the first of the Senshi for Usagi to befriend certainly helps.
To Love Ru has Mikan, the main character's little sister, as one of the most mature characters in the cast. Except for not hitting puberty yet, of course.
In the flashback arc of Trigun we get young Knives. Levelheaded, charming, genius programmer—one year old. He's also got a fair helping of cynicism and subscribes increasingly to a utilitarian philosophy, which eventually propels him into deciding to Kill All Humans. But hey. He was unreasonably wise all the same.
Their response to the Tesla revelation is electing to sit down right there and stay there until they die, rather than running to their mother figure and if not asking her for comfort at least confronting her about her betrayal. Tell me that's not unchildlike.
Manga Wolfwood was shot for the first time when he was eight or so, and suddenly realized that he wanted to live, after all. Anime Wolfwood was abused and offed the bastard at a slightly older age.
Manga Wolfwood was subjected to medical treatments that aged him at an accelerated rate, and based on the ages of the other kids in the orphanage in the flashback and when he returns, he can't be older than eighteen when he dies, which makes him no more than sixteen when he met Vash. So he's kind of this for the entire series.
Little Legato is somewhere between eight and thirteen, probably on the younger side, but his response to Knives appearing and killing everyone but him, including the building they were raping him inside, is… uniquely calm, to say the least.
And possibly Zazie the Beast, anime version. Or he may be an adult with a hormone condition. Data insufficient.
Every kid on this list except Vash is also under Creepy Child.
Rihoko in the Witchblade anime, to the point of being smarter than her mother.
Chiru from Xabungle is all of 8 but consistently manages to be one of the more level-headed characters in a cast of teens and adults. This is significant, since in 1981 children in anime, if they weren't the main character or in a cast of mostly kids, were typically The Load or a Bratty Half-Pint.
Seto Kaiba from Yu-Gi-Oh! He pretty much threw his childhood in the dumpster when he promised to always take care of and protect Mokuba. The fact that he rarely smiles and is exceedingly serious, not to mention he runs his own company, despite being only perhaps in his late teens/early twenties is actually commented on by several of the characters, notably Joey, Tristan, and Tea. Plus, the guy beat a chess grandmaster at age twelve, and then proceeded to turn ten thousand dollars into about ten million dollars in the course of one day, when he had a year to do it.
