Il-ho, the satellite 'KITSAT-1', is launched into space. She observes Earth and becomes curious about the human heart. Kyung-chun, an aspiring musician, is heartbroken and turns into a milk cow when his longtime love interest, Eun-jin, starts to date another guy. Then, one day, Kyung-chun is attacked by the Incinerator which tracks down those with a broken heart. At that moment, Il-ho falls from space and becomes human by magical forces. And she ends up staying at Kyung-chun's place. Gradually, the two become close and Il-ho begins to slowly understand the human heart.