Topic on Category talk:Trope Workshop
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There's also the requirement that a character's age must be explicitly stated in the work. Nausicaa's age is given as sixteen by some sources, however this is not confirmed in the film or manga, so it doesn't qualify. If the age is not stated, the examples should go to Kid Hero.
The trope is designed specifically to appeal to teenagers, while Kid Hero can appeal to pre-school children, pre-adolescent children, and teenagers. It can be used to frame a more mature work, like in Neon Genesis Evangelion.