Orphan Himari Momochi's only link to her late parents is the house they secretly bequeathed her, which she does not learn of until her 16th birthday. Thrilled by the opportunity to know more about her family, Himari arrives at the rumored haunted house and is bewildered to find three young men already living there: Aoi Nanamori, who identifies himself as the guardian of the place, and his two familiars, Yukari and Ise. Although they allow her to stay overnight, they warn her to leave the next day so she can avoid harm from ayakashi—wandering spirits that sometimes attack human beings.
Surprisingly, Himari is unaffected by her spectral encounters and determined to move in to the residence. After she discovers that Aoi had become guardian unwittingly and is now confined to the property, forgotten by the outside world, her resolve only grows stronger. Touched by his story, Himari decides to find a way to free Aoi from his dim fate, and she convinces the three Momochi House protectors to accept her as their landlady. However, the mysterious Kasha who keeps sending hostile ayakashi to Himari's new home seems to have darker plans for Aoi's future.