Wi Mary (Mun Geun-young) is the cheerful, pragmatic daughter of a failed businessman who had grown used to being constantly on the move to escape from debtors. She becomes fast friends with the free-spirited singer Kang Moo-kyul (Jang Keun-suk) when she nearly ran him over in a car. Meanwhile, her father Wi Dae-han is saved from his debtors by his old friend, Jung Suk (Kim Jae-wook) who had just returned from considerable success in the Japanese entertainment industry. Jung Suk, who had harboured a secret love for Mary’s mother, sets up a deal with Dae-han to have Mary marry his son, Jung In. In her desperate to escape this predicament, Mary begs Moo-kyul to pose as her husband, and finds herself in even more trouble than before when her father proposes a 100-day period in which she has to divide her time equally between Moo-kyul and Jung In, after which she has to decide who to marry.