With age comes wisdom and experience, at least most of the time. Maturity can come naturally to some, but not for everyone. It can be easy to act immature, but there's always a time when that attitude won't cut it and a more serious attitude is needed. That's where certain people end up displaying levels of maturity nobody thought was possible for them.
In anime, there are a lot of characters who act immaturely, though when there's a lesson or situation that demands them to act mature, they can rise to the occasion. A lot of the time, immaturity can be a mask they put on to hide their true strength or self.
10 Ash Realizes The Value In Losing (Pokémon)
Pokémon's Ash Ketchum is not exactly the most mature character across the anime's long history, and that's understandable considering he's been ten years old for quite some time. Ash is often learning the same lessons over and over again, but the one that seems to stick with him is his attitude about losing.
While he's down and out about his first major Pokémon League loss, he's grown past feeling upset about it and has taken his other league losses with faith that he'll win the next one. Accepting a loss can be a hard thing for anyone to do, but Ash learned how to not only accept losing but also stay positive in the face of it.
9 Happy Tells The Exceed, "We Are Not Your Puppets!!" (Fairy Tail)
Happy is Natsu's best friend and trusty flying sidekick, and believe it or not, he's also a mage of the Fairy Tail Guild. More often than not, Happy acts immaturely, and he's one of the many comic relief characters in Fairy Tail. That being said, Happy isn't just a joke machine and can get serious in the right situation.
One great example of this is during the Edolas arc, where both he and Carla learn that they're originally sent to eliminate Dragon Slayers. As Carla breaks down in tears, Happy rejects this truth, telling the other Exceed, "We are not your puppets!! We are Mages of Fairy Tail!!" This shows how loyal Happy is to his friends and that he's willing to defend them.
8 Dazai's Emotional Wisdom Shows (Bungo Stray Dogs)
Bungo Stray Dogs' Dazai is a complicated character. While he's often messing around with his fellow members of the Armed Detective Agency or various life-threatening activities, he's also incredibly smart. He's also willing to give his teammates advice if they need it, like when Atsushi learns of the death of his orphanage's director.
Atsushi feels conflicted in his feelings about the news since the director does some admittedly horrible things to him in the past yet wants to congratulate him on his accomplishments. Dazai validates how Atsushi feels, telling him that it's okay to feel either sad or unforgiving about his father figure.
7 Subaru Admits His Faults (Re:Zero)
Admittedly, it takes some time for Re:Zero's Subaru Natsuki to grow past his initial immaturity and hero complex in the first season. After a string of deaths ending in failure, Subaru tries to run away from his problems, but Rem tells him that it's not like him to give up. In response, Subaru finally breaks down and admits to his own shortcomings.
Despite it being a rant full of self-loathing, Subaru shows some true humility for the first time. And despite his flaws, Rem lifts him up and gives him a much-needed pep talk, which becomes the starting point for his true character growth.
6 Koro-Sensei Gives His Students Some Wise Advice (Assassination Classroom)
Despite his happy face and goofy demeanor, Koro-sensei from Assassination Classroom shows his students that he can become really scary if he's pushed far enough. With his abilities, that makes him all the more terrifying. Still, even in that state, Koro-sensei is still a teacher who is able to deliver some wise advice when needed.
One example of this was when the students of Class 3-E accidentally injure an old man while trying to hone their assassin skills. Some of them try to justify it with all the pressure they're under, but Koro-sensei tells the class that it's best not to forget about empathy after becoming stronger.
5 Bakugo Learns The Truth About All Might (My Hero Academia)
Usually, My Hero Academia's Bakugo comes off as prideful and agitated, believing himself to be the strongest and the best out of Class 1-A. He's not exactly the type to admit to his insecurities, but he is capable of it. Bakugo challenges Deku to a fight, and his resolve changes when Deku sees a more vulnerable side of his old friend.
It's here that Bakugo breaks down, revealing that he realized the truth of Deku and All Might's secret while letting out all the anger and frustration he's been holding within himself. He even blames himself for being captured and All Might's retirement.
4 Satoru Gojo Is Ready To Burn The Jujutsu World To The Ground (Jujutsu Kaisen)
Despite being the mentor to the first years of Jujutsu High, Jujutsu Kaisen's Gojo doesn't exactly act like a teacher. He often acts more childish than his students and doesn't seem to take anything seriously. That being said, Gojo is wise in his ways even if it appears that he's just messing around.
After Yuji meets a temporary demise, Gojo gets serious while admitting his hatred for the higher-ups of the Jujutsu world who orchestrated it. While he's strong enough to kill them all now, nothing will change, so he decides to put it all on his students. Gojo wants to burn down the Jujutsu world as it is now, but he knows the best way to do that is to prepare the next generation for it.
3 Luffy Declares War For The Sake Of A Friend (One Piece)
One Piece's Luffy is as immature as protagonists come, though there are times when Luffy actually puts that attitude aside and displays some maturity. One of the best examples of this is during the Enies Lobby arc, where he and the other Straw Hats declare war on the World Government in order to save Robin.
While he's warned that doing so would put a target on their backs forever, Luffy isn't afraid of taking on the world even if it's to save one friend. He inspires Robin to keep living and moving forward.
2 Goku Makes The Ultimate Sacrifice (Dragon Ball Z)
Goku is a pretty irresponsible guy throughout the entire Dragon Ball franchise, but there have been times where he's been able to take responsibility for his actions, sometimes at the cost of his life. A prime example is during the Cell Saga when he sacrifices himself to save the Earth from Cell's self-destruction.
Without even saying it, Goku is making up for his mistakes and putting everything on Gohan. He bids his son a heartfelt goodbye while telling him to take care of his mother before teleporting away. It's probably the most mature thing Goku's ever done, followed by his request to remain dead to protect his loved ones.
1 Jiraiya's Last Stand (Naruto: Shippuden)
When viewers of Naruto first meet Jiraiya, he comes off as a pervert and a goofball despite being a good teacher to Naruto. As time goes on, his strength and spirit are proven again and again, but Jiraiya shows the most maturity at the end of his very life. Battling his former student, Pain, Jiraiya has the chance to run but stays in order to unravel the truth about him.
Jiraiya soon accepts his death with dignity and a smile on his face. His final thoughts are of Naruto, with faith that he is "the child of prophecy" and how his ninja way of never giving up is much like his.