The Demon Prince of Momochi House

Himari Momochi inherits the Momochi House on her 16th birthday, a mansion that's all that remains of her biological family. Raised in an orphanage, she initially dismisses rumors about the house's supposed haunting, but things take a turn when she meets Aoi Nanamori and his companions, who are occupying the mansion without permission. Himari's decision to stay results in a series of events, including an attack by youkai, which leads her to discover that the house is a nexus between the world of the living and the spirit realm. Aoi, who has been designated as the house's guardian, is bound to the mansion and has had his human existence erased, prompting Himari to vow to help him break a powerful curse.