When she gets home from highschool, Guest’s estranged older brother, Dmitri, is at the door. He tells Guest that their father, who left at birth wasn’t actually human. He was a demon, an incubus to be precise, a demon that feeds on sex and desire. That makes Dmitri an incubus as well, and makes Guest a succubus. Guest’s father, Zarakos, wants Guest to move in with him and Dmitri and learn how to be a good demon, and a good Succubus.