Kasuki is a handsome guy who goes to college and has nightmares about a sex demon. He thinks he's having these nightmares because he's playing a video game called "Magical Girl Lapi-chan", but one day, his dream girl Joran asks him to destroy this sex demon. That's when Kasuki realized that this demon was slumbering in him. Later, Joran approaches the other guys with the same request, i.e., to stop the demon in Kasuki. They start blackmailing him by raping his older sister Fauna. It is at this point that the little devil Kuroto, who is also after Kasuka, is unleashed.