Blue Exorcist: Season 1, Episode 11

1 - 11: Demon of the Deep Seas

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.