On her sixteenth birthday, orphan Himari Momochi learns she has inherited her late parents' house, only to find it already occupied by three young men, including the guarded Aoi, who is bound to the property as its ayakashi guardian. Momochi House sits on the boundary between the human and spirit worlds, and Himari is expected to take over as its next protector despite knowing nothing about the ayakashi crossing over from the other side. As she settles in, she starts unraveling why Aoi is trapped there and what the house is truly guarding.