Uh... Well, let's see here, shall we?

First off... That personality is SUUUUPER bare-bones right there. Need more fleshing out on that.
History... Well, if you're going to say that he won't say anything about them, then proceed to make an offhanded comment about what actually happened... Some kinda disjoint there. Also, there's no reasoning for his abilities thereafter. i'm assuming this is an original world, so yeah.
Abilities... I don't know if someone can become adept at multiple weapons by the age of 19 and be picked up by a bunch of assassins and trained without any logical reason behind it.

I can't say much else because there's not much substance to talk about in the first place.