Your grandmother's home — a European mansion full of old stories — has passed to you. Moving in on your own seemed straightforward until you discover that her fairytales were not fiction. By accident you release three demons who had been imprisoned there for fifty years: a siren, a vampire, and a werewolf. They immediately become entangled in your life, alongside three schoolmates (a cheerful underclassman, an aloof senior, and a childhood friend) and one more figure kept half-secret. All of them are competing for your attention in what the story describes as a "Miracle Cohabitation."