Bullied and brilliant student Ideo Hazama attempts to summon a demon from the Expanse to exact revenge on his tormentors. The summoning goes wrong and Hazama is possessed by the demon, declaring himself as the "Demon Emperor" and throws the school into the demon's realm. The protagonist is among those trapped in the school, along with fellow students Reiko Akanezawa, Yumi Shirakawa, Shinji "Charlie" Kuroi and Akira Miyamoto. Should the protagonist side with Yumi or Shinji, they navigate the demon-infested school and towers.