14 years old.  

Daniel looks a little old for his age, which- along with some decent clothes- keeps anyone from questioning whether he has a home. He has brown hair, about down to his earlobes, and green eyes.  

Daniel's power is sound manipulation. This can manifest itself in every way from amplification to pitch alteration, but he tends to make use of it in other ways in combat. He uses instruments, primarily an electric guitar, to use these powers in battle. He theoretically could do it using any noise, but the instrument acts as a focus, as (similar to most supernatural abilities in fiction) he can't use them without a clear mind, and a battle is a hell of a place to achieve concentration. Chord types correspond to their effects; a minor chord, for example, is a malevolent effect, while something like a D7 would have a more neutral effect, and an F chord would be benevolent.  

As for his life, he's an orphan. No one really ever figures it out, since he gets a decent amount of cash from playing on street corners, and occasionally getting a legitimate gig in a bar or something. Still, you can't live on the street for your entire teenage life without the government eventually finding out, so he's taken the Academy as his home.