As an average student, Kosaka always wondered what it would be like for girls to fight over him. But now his girlfriend Shizuka and his friend Kasumi are fighting over him...with swords. His school has a secret, a black gate that can only be opened by Shizuka and Kasumi, who each have a tattoo over one of their breasts. When Shizuka opens the gate and makes a deal with the evil creatures on the other side, Kosaka and all the other girls at his school are thrown into a deadly fight against evil.