Dating Sim game master Keima Katsuragi isn't interested in any girls who are not 2D. After accepting an e-mail challenge, he soon discovers he's made a deal with a not very competent young female demon, Elsie de Lute Irma. She's been charged with recapturing runaway demon world spirits hiding in a girl's heart who can only be driven out by the girls falling in love with Keima. Now he must convince girls to fall in love with him within a specific time limit. If he fails, the explosive collars around his and Elsie's necks will detonate.