Nicaea, a website that delivers videos of dead faces, shows its users footage of their friends' deaths. Most people register on the site for trivial reasons, including Io Nitta, Daichi Shijima, and Hiro Kageyama. As the three students return home from a mock entrance exam, they simultaneously receive a message from Nicaea depicting their gruesome fate in a subway station. Although shaken by the email's contents, the trio ignores it until a subsequent earthquake and train derailment cause the premonition to come true. Swallowed by darkness, Io is faced with a simple question: does she want to die, or would she rather live? Demonstrating a will to live, Io wakes up in the rubble alongside Hiro, Daichi, and mysterious entities who ask the three of them to "manage" them properly. Soon, they find themselves in the custody of JP's—a mysterious defense force that only operates during a national state of emergency. After making contact with the otherworldly beings that attacked them earlier, the three students learn that they are now "devil summoners." The Earth is under attack by "Septentriones," strange creatures hellbent on destroying humanity. With their fates now intertwined, Io, Daichi, and Hiro must work together to protect what remains of their planet before being completely obliterated.