After learning that one of their students, Rin Okumura, is the son of Satan, the ExWire of True Cross Academy are filled with astonishment and horror. But, for the time being, they are more concerned about something other than Rin's parentage: the Impure King's left eye, a powerful demon, has been taken from the academy's Deep Keep. Rin and the other ExWires are dispatched to explore the mystery surrounding the Impure King and the thief's ultimate purpose when an attempt to steal the right eye is attempted in Kyoto as well.