Your avatar is cool. :o It looks like an creature that would be a small enemy. And then maybe later in a stage the grey version would pop out and be huge. That'd be the boss fight.
@Xdqwerty, Osu! Tatakae! Ouendan! is the Japanese version of the game, different settings/characters/songs but otherwise identical mechanics. I played that before I knew about Elite Beat Agents lol. Both fantastic games https://en.wikipedia.org/wiki/Osu!_Tatakae!_Ouendan