For some reason, Shirakawa Yuu has been living with his grandparents, but he is supposed to live with his mother after an interval of more than ten years with her new husband, that is, his step-father. There, his step-sisters, Shirakawa Kyouko, Ryouko and Anzu, who have grown to be very beautiful women, are waiting for him. The sisters welcome him, and let him use the room of their father who is always absent because of his archaeological studies. In the room, he finds a queer jar. It is a cursed jar that will cast upon him the worst of curses unless he collects women's love juices within a limited period of time.