Rin, Shima and Izumo have been sent on a mission, only to end up working instead. They meet a boy named Yohei and learn of the "Demon of the Deep." Yohei lost his father to this monster, and wants revenge. Worried, Rin and the others watch over him.

Senior Exorcist First Class Shura Kirigakure stops the battle between Rin and Amaimon. Rin learns that Shura was once a disciple of Shiro's - and that Shura has targeted him for elimination - "the job that my mentor failed to do!"