After discovering that he is a uniquely powerful Geist-infected human, Hiroki forms an uneasy alliance with Shion, a dimensional "Doll" designed to hunt his kind. However, their relationship is put to the test when Shion is captured by a sadistic Slug Geist who uses a pleasure-inducing serum to torture her for information. Just as Shion reaches her limit, the mysterious leader of the Geists, Miko, makes a sudden appearance.