Fill Me Up, Mr. Assistant!

During the day he’s an administrative university assistant but by night, Shin Dowoon works as a demon hunter. Before him appears the promiscuous incubus in the form of a human student named Lee Hayoon. Hayoon offers a contract in return for letting Dowoon capture him. But because of the devil's tie-up play, Dowoon has no sympathy. Will this rough play be enough to satisfy the demon?