The main characters, two shrine maiden sisters named "Kaguya" and "Setsuna," were living a peaceful life. However, their life changes dramatically when the seal of a powerful demon clan is broken. This demon clan was once a ferocious family that devoured most of humanity. With their revival, humanity faces a crisis. They are trying to eradicate almost all of humanity. Only "Kaguya" and "Setsuna," who possess the power of the seal, can reseal them. The fate of humanity lies in the hands of these sisters. Can they indeed save humanity!?