Ritsu Kidou, an ordinary office worker, is the descendant of an exorcist who makes a contract with the devil and exorcises demons. One day, he wakes up and is confused to find a used condom in his hands. Looking around the room, he sees a naked man with horns and wings glaring at him while covered with a blanket.

"Don't tell me you've forgotten! After summoning the king of the demon world, Ryan... he did that... that...!!"

Holding his head, which hurts from a hangover, he recalls the mistake of one night. Where will the two of them go as they struggle to break the tightly bound master-servant contract full of mistakes? A pure love romantic comedy about a master-servant contract between an ordinary office worker and a proud tsundere demon king is born!