Strange things start happening to Asano Shinichirou, a second year student. A woman turns into a centipede, and he sees a girl is attacked by a monster. During all the chaos, he runs into Shimadzu Sakuya, who uses a bow as a weapon. She is the 37th head of the Shimadzu family, tasked with ridding the world of monsters. Shinichirou and Sakuya end up fighting one of the monsters together.