Tsubomi Ibara, a normal juvenile delinquent who's being threatened by a bunch of senior immature delinquents. What if one of them is...something dangerous? Luckily there's a slayer to exorcise the threat and he becomes one of the Magister! But as a succesor of a creature that could destroy and "cleanse" the world, contained in their protection and an attempt to restore his humanity. Can he become a normal human again despite the missions and invasions that try to disrupt in restoring his humanity?