Minase, a high school student, found a magic book in a secluded room at his school. He began practicing black magic, which has extreme sexual effects that benefit him and some of his friends. Intrigued, Minase delved deeper into the art, unaware of the evils that lay ahead. Eventually, the book's origins were revealed, as well as the incident that occurred twelve years earlier on Walpurgis Night, the night when the power of evil is at its strongest. After regaining his senses, Minase struggles to escape the darkness he had plunged into.