Every school has secrets, but few leave a stain that won't wash out. In a certain school, there was once a fun club centered around magic but had turned into murder and a lust for power. Sealed and willfully forgotten, the resulting evil of that day remained chained in the school's basement. Twelve years later, high school student Taki Minase, while inspecting the place where the incident took place, uncloaks the secret plastered in blood—a book of magic called Black Bible. Trying his luck with its love curses, he soon finds out the magic proves real and easily penetrates the hearts and bodies of his fellow classmates. The resulting intercourse leaves the student body very vocal, and Minase's acts do not go unnoticed. What was at first a simple stroke of curiosity becomes much larger and harder to control. Fully swallowed by the unshackled darkness, everyone he knows becomes a victim, including his childhood friend Kurumi Imari. Torn apart, Minase finally realizes his mistakes and that he must reverse them in time if he ever hopes for him and Imari to come together.