what is the deal with the japanese obsession with very young main characters in

[redwolf481]

anime and video games? in ffVII squall was 21 and saved the world, ffvIII squall was 17(both had the body and mentality of someone older) in FVXIII lightining is barely 21 but shes has the mentality and body of someone to me in their late 20s early 30s...spike spiegal is 27 and a guy whos been in the army, mafia and is now a bounty hunter and has the mentality and physicality of someone much older...in ergo proxy the lead female is 19 high ranking detective and sounds like a 30 year old and looks like one and sounds very sure of herself...they all share that in common with many other animes...what is the deal with this,,,