Late Teen Hero

Love them or hate them, teenagers are things that exist. They often end up as the protagonist of a lot of works, especially in Anime and Manga. Using a teenage protagonist is effective because it reflects the target demographic of a lot of shows. They also allow the exploration of some mature themes, such as loss, grief, and mental stress. Both kids, teens, and adults can relate to a teenage protagonist. Young kids can see themselves as a teen in a couple of years. Adults can think back to their teenage years. No wonder why the trope Kid Hero is so popular!

The Sister Trope Early Teen Hero deals with twelve to fifteen year olds, as that is the range where a character is the most relatable. That range does post some limitations, though. It prohibits you from exploring some mature and adult themes, particularly those involving blood and gore. Audiences will be left wondering exactly why a character so young is experiencing such things, and pondering exactly why you as a creator are letting someone so young experience such things. Sure, that never stopped shows like Neon Genesis Evangelion, but it's best to be on the safe side.

The Late Teen Hero, thus, deals with a different age range, between sixteen and nineteen.

Sister Trope to Early Teen Hero. This trope has a lot of overlap with Kid Hero, although the heroes may be too old to be considred a "kid", and many older heroes aren't kids at all.

Anime and Manga

 * Studio Ghibli
 * The Cat Returns has the seventeen year old Haru.
 * Porco Rosso has the seventeen year old Fio Piccolo.
 * From Up on Poppy Hill has the sixteen year olds Umi and Shun.
 * Tales From Earthsea has the sixteen year old Therru.
 * According to storyboards, Ashitaka from Princess Mononoke is seventeen years old.
 * Sophie Hatter in Howl's Moving Castle was eighteen. Was eighteen. The trope is only briefly used, before she is cursed to become a much older lady around ninety in age.
 * Nausicaä in Nausicaä of the Valley of the Wind (both anime and manga) has an age which falls around this range. The age is never officially stated, though, although some sources cite it as sixteen.
 * Almost every single student attending the Luna Nova Wizarding School in Little Witch Academia is sixteen years old.

Literature

 * A borderline example is in House of Many Ways. The main character Charmain Baker is implied to be around this age range. She's old enough to be sent away to look after a house on her own, indicating she is at least sixteen to be able to take on such a responsibility. However, in an Exact Words letter, she indicates that she is of age without specifying exactly what age she is of. The intended interpretation for the letter--which is false--is that she has come of age, and is at least eighteen. This is implied to be false, putting the upper boundary of her age at seventeen.