Rumor has it that teenagers who have committed a terrible misdeed in their life will go missing. These young criminals are taken away and never heard from again.

When Yuuki Oku awakens, he has no memories and is being driven to a remote school in a car. After arriving, he is led into a classroom. Only six other people are inside. To his horror, he learns that everyone in the room is a criminal, including himself. As students of the class, each and every one of them is incomplete. Whether it's a limb, a heart, an entire head, or—in Yuuki's case—memories, they have all had something vital removed. Though there are seven people in the class, they are told that one of them is not human, but a puppet constructed from their stolen body parts.

To escape, Yuuki must first earn the right to graduate in a week's time. But even if he does, he must also identify which of his classmates is the puppet and take back what was once his.