Kouta is a student just getting started with college. He’s looking forward to living in his own house, reuniting with his cousin Yuuka, and generally living an uneventful life. But plans change as one evening at the beach, they find a strange, naked girl with horns growing from her head. She has no memory of who she is, and can’t even speak, so naturally, they take her in. “Nyuu,” as they call her, has a dark, terrible secret. She’s actually a Diclonius, a human with special destructive powers. A powerful organization is trying to hunt her down, but Kouta’s strangely protective attitude towards Nyuu gets him and Yuuka entangled in mystery, intrigue, melodrama, and lots and lots of bloody murder.