Kyungcheon is a pianist-in-training who loses his heart and becomes a milk cow. He lives as a man during the day, but becomes a milk cow at night and eats grass. Meanwhile, with the help of wizard Merlin, a satellite named Ilho fell from the cosmos by a supernova, is transformed into a girl. One day, Kyungcheon is attacked by members of a secret agency that chases people who lost their heart. Kyungcheon defeats them with the help of Ilho. Following a narrow escape from secret agents, the two mismatched characters come to know about each other’s secrets and draw close.

A nebbish schoolteacher begs his smooth (and misogynistic) pal to teach him 'the knack' – how to score with women. Serendipitously, the men meet up with a new girl in town, as well as a friendly lunatic who can’t help but paint things white.