Coelacanth Satomi’s entire high school is assembled in the auditorium for the announcement: her old math teacher has been murdered. The news causes her classmates to burst into tears, but the girl remains stoic, even in the face of the rude sheep that she hallucinates. But her apathy doesn’t stop her from getting sucked into the case: she becomes acquainted with Yukinari, who the police believe is involved with the murder. This man reminds Satomi of a boy in bloodstained clothing that saved her life ten years ago, when the apartment building that she lived in exploded under mysterious circumstances. And though that case remains unsolved, as time goes on more and more threads are discovered connecting it to the recent murder; just how are these two cases related?