The story is based on the Izumo cycle of Japanese mythology and the tale of the god Susanoo and the eight-headed monster Yamata no Orochi. The main character, Momiji Fujimiya, is a descendant of the mythical Princess Kushinada . When Japan is menaced by Aragami spawned by Yamato-no-Orochi, Momiji is intended to be sacrificed to appease the Aragami. She instead, however, becomes a member of the Terrestrial Administration Center (TAC), a secret agency charged with fighting them.