The protagonist, Hikaru Touma, attends a prestigious school with a historical past, the Izumo Private School. He and his friends (mostly girlfriends) are into various kinds of martial arts. One day Hikaru wanders into an old school building and finds an altar there that he once saw in a dream. Hikaru touches the mirror that lies on the altar and gets sucked somewhere, accompanied by a violent flash of light and an earthquake. After the earthquake ends, he hears the screams of his acquaintance, Nanami Minase, a junior high school student and member of the archery circle. He rushes to her aid, and sees that she has been attacked by a spider the size of a dog, and has already entangled her with its web. Hikaku meets the danger face to face, and frees Nanami. Hikaru, even though they are still in the school building, notices that the atmosphere is not what it used to be: no birds chirping, no voices of people, and the entire campus seems completely deserted. But this is just the beginning of the adventures of these two characters…