The player's grandmother told wonderful fairytales, and her old European-style mansion holds warm memories. When the chance comes to live there alone, it seems like a pleasant chapter. It turns out the grandmother's stories were not entirely fictional: within the first day, the player accidentally releases three demons who have been imprisoned inside the mansion for fifty years — a siren, a vampire, and a werewolf. These three, along with three schoolmates (an energetic underclassman, an aloof upperclassman, and a childhood friend) and one additional secret figure, all begin competing for the player's attention. The Miracle Cohabitation Story has begun.