Matteo a fait un pacte contre les hommes, a quitté la ville pour une nouvelle ville avec 80% de la population a plus de 60 ans et a évité les hommes à tout prix. Mais cela arriverait-il si un nouveau voisin sexy se présentait de manière inattendue ?
Tatsuki and Ohta are two beings from a supernatural, mythical realm, masquerading as "cousins" in the human world. Tatsuki is in fact the successor to Ryu-Oh, the dragon king, and possesses the power of the Nyoi-Houshu, a magical dagger. Ohta is a Zashiki Warashi, a protective house-spirit without a home, and is also Tatsuki's subservient lover. When their human classmate, Kouhei Misaki, accidentally witnesses the two having sex, he mistakenly believes that Tatsuki is forcing the quiet Ohta into it, and he resolves to break the two apart.