The anime characters are always young. Very young. And they tend to have the average age of 15, unless the character is a soldier then they would be 18. Those characters will usually have multiple weapons and magic on them just for the plot.

For example, Killua Zoldyck from Hunter x Hunter has the ability of an assassin at the age of 12, or Sakura Kinomoto from Cardcaptor Sakura who has magical card abilities at the age of 9!!!

Anime: Hunter x Hunter