Leo Aoi looks like a crazy animal with wild eyes, and he goes berserk whenever he feels threatened and sees blood. That doesn't stop animal-lover Yuiko Kubozuka from befriending him, however. In fact, Yuiko is the only person Leo will listen to when he has one of his violent fits...

Leo's 18th birthday is around the corner, but celebrating seems impossible as someone is after Leo's life! Can Leo overcome the dangers of his past? Or will this beastlike boy be separated from his beloved master...forever?