This is just cool. Fine, the DS homebrew app is from Japanese coder Tarosa, but music always transcends language barriers. That and it's got the sexy Hatsune Miku character sprite.
Innocence is based on the Hatsune Miku vocaloid synthesizer software. What the hell is that? Well, think of it as a program that you input to and it churns out a synthesized song, with Hatsune Miku singing it - wiki it if you have the time.