Yoru is the villainous tritagonist of the Academy Saga. She is the War Devil who embodies the fear of war. She is a member of the Four Horsemen, who now occupies Asa Mitaka's body as a Fiend. Following her taking over Mitaka's body, Yoru sets out to locate Chainsaw Man, whom secretly attends the Fourth East High School with them. She also coerces Asa into looking for a target to seduce and turn into a weapon.