Ganta Nakami is a high school student who suffers from insomnia. He meets Isaki Magari, a girl with the same condition. A relationship forms as they share a secret and catch up on their sleep in their school's abandoned observatory.

Ootsuji Detective Agency has a new case. Now, facing the strangeness of the "mass disappearance" bewildering society, Detective Soutarou takes the investigation head on!.