After a sinister occult ritual in a school chapel turns students into mindless sex slaves, the administration attempts to cover up the incident to protect the school's reputation. As a lonely student named Shion discovers a kindred spirit through their shared interest in forbidden books, a specialized investigation is launched to uncover the dark magic and depravity haunting the campus.
Ichijou Nozomi returns to his alma mater, the School of the Holy Spirit, undercover as a teacher to investigate a series of ritualistic attacks. He discovers that a student named Mutsuki Jouji is using dark magic and sexual dominance to build a cult-like following in pursuit of total control over the school. As Ichijou gathers evidence of black magic, he becomes a target of suspicion for Mutsuki's devoted followers.
As investigations into a series of disturbing incidents at the school continue, the focus shifts to the mysterious influence of a "Master" who uses hypnosis and brutal "purification" ceremonies to enslave students. Midaigawa Shion, a girl once fond of literature, finds herself caught in a web of forced adoration and manipulation, while the dark truth behind the school's power struggle begins to surface.