Man Child: Anime and Manga

  • Aoi from Aoi Destruction is 38 but looks prepubescent and acts like an elementary schooler.
  • Axis Powers Hetalia; yes, new viewers, the character throwing a tantrum and beating a dragon with a Hello Kitty doll is a four-thousand-year-old man.
  • Death Note:
    • L sits like a kid, eats a lot of sugar, playing with his food, and in the anime, after hearing something important, ran and dove head first on the couch like a ten year old boy would.
    • They give the reason for his sitting position being that the brain gets the most oxygen from that posture. His liking of sugary foods has been explained in special material as being necessary for his brain, which burns calories like mad.
    • Near. He's 17-18 in the post-timeskip (21 in the post-series one shot) and he's always seen playing with toys.
  • Dragon Ball Z:
    • When there isn't something to punch, Goku embodies this trope, often acting less mature than his granddaughter.
    • The Ginyu Force would qualify, playing jan-ken-pon to see who gets to fight who, and betting chocolate bars on the outcome of fights.
    • Android 17, in all his fascination with his own personal entertainment, is the kind of Psychopathic Manchild that borders on this trope.
  • Amarao from FLCL is a subtle example, established early on when it's revealed that he has a serious Sweet Tooth and hates spicy food ("spicy = adult and sweet = kiddy" being a recurring motif in the series.) He spends his whole time in the series trying to turn Naota away from his Coming-of-Age Story Character Development, and Word of God confirms that he's basically an older version of Naota without said Character Development.
  • Milla Ackerman from Godannar before regaining her full memories.
  • Usagi from Junjou Romantica appears to be this. He's actually trying to simulate a child's environment because he wanted to "recreate what normal kids do in their childhood".
  • Apachai Hopachai in Kenichi: The Mightiest Disciple is known as the "Death God of the Muay Thai Underground" and is a deadly fighter in combat. Outside combat, however, he's very innocent, gentle, and childlike.
  • Galactic otaku Keroro Gunsou is this - followed Pekopon anime as a child, then subjected to Training from Hell until he was assigned to Pekopon to lead the invasion... making it far easier to follow his old hobbies as a result. Just picking up where he left off in life.
  • King Dedede in Kirby of the Stars, he tends to act childish, constantly whines and demands his way and orders monster to sick on the Cappy's and Kirby For the Evulz.
  • Misato from Neon Genesis Evangelion. Downplayed, and played for tragedy instead of humour.
  • Doctor Tokita in Paprika.
  • Figure skater Azusa Shiratori from Ranma is a spoiled 16 year old girl who acts like a 5 year old, she'll steal anything she considers cute even if it's just a food item and she will give it a pet name, if the person who has the thing she wants won't hand it over she will attack them with anything she can find.
  • Naki from Tokyo Ghoul. Emotionally immature, easily confused, and surprisingly childlike when he isn't being psychopathic. He frequently misunderstands conversations, is prone to screaming/crying meltdowns, and at one point proudly explains that he is writing a letter to his beloved Cool Big Bro in Heaven.....and it will be delivered as long as he addresses it to "Heaven". While an antagonist, he is portrayed as one of the most sympathetic characters due to his childlike nature.
  • Maximillian Pegasus from Yu-Gi-Oh! uses a toon deck, and all his duel talk is about his favourite children's cartoon based around a rabbit. He also loves cartoons. A lot.