In the Edo period, at the remote village of Okitsu, the evil cult leader Koushirou uses ninjutsu to ensorcel sharks and forces them to attack local pearl divers so the cult can steal the pearls from their mangled corpses. Desperate for help, the village chief hires Kotaro Shiozaki, a guard at a nearby temple, but Kotaro soon finds his path blocked by lady ninja Kikuma, and a gigantic shark that doesn't seem like something from this world.