Souta is erotic. There live three girls next to his house and he knows all of them well. His parents are now abroad on business, so he is taken care of them. On Arisa’s birthday, they tell him that they are daughters of the Devil. Souta isn’t surprised to hear that. They are relieved and tell him why they live in this world. Their purpose is to find a partner and prevent extinction. They suddenly order him to choose a partner out of them….