On her 16th birthday, Himari Momochi receives a letter stating she has inherited a mansion called the Momochi House. Having been raised in an orphanage, this mansion is the only thing left of her real family, so Himari pays no mind to the rumors that it may be haunted. Upon entering it, she meets Aoi Nanamori and his companions, Ise and Yukari, who all seem to be squatting in her new home. Although they warn her to leave the house, Himari vows to be the one to make them leave instead.