During the Feudal era of Japan, Kakizaki Kocho was known as the demon princess for all the kills she'd made for her lord of the Uesugi family. She was a historical figure lost in the timeline until now when Oka Haruhiko, a college freshman in Tokyo who was back home for summer break, accidentally breaks the small shrine in the forest and releases her spirit. Kocho slowly materializes into physical form as she haunts Haruhiko for days until both sides understand what sort of circumstance they are under. Now Haruhiko has an ancient female warrior as a roommate and his life is going to get really complicated.