玛丽外宿中

魏玛丽（文根英 饰）因父亲被骗欠下巨额债务，一直过着躲躲藏藏的生活。不靠谱的父亲每天被债主追的四处逃亡，只能偶尔回来看望女儿。玛丽被迫卖掉了家中所有家具，只留下了一台电视。平时靠打打零工和给别人当“代理司机”谋生的她，因一次意外车祸，认识了地下乐团的主唱姜无缺（张根硕 饰）。不打不相识的两人竟然喝的酩酊大醉，还一起睡在了玛丽家里。从此姜无缺接二连三借宿玛丽家，让玛丽的父亲非常恼火。玛丽父亲意外遇上了失联多年的有钱朋友郑石，为了摆脱债务，他擅自答应了郑石，要把女儿嫁给郑石的儿子郑仁(金材昱 饰)。甚至偷了玛丽的身份证跟郑仁登记结婚。玛丽为了反抗与无缺拍了结婚照，假装已经结婚。郑仁也同样反感父亲的无理要求，为了摆脱困境他向父亲提出他和玛丽、姜无缺，三人100天的古怪试婚要求，希望100天后父亲能够知难而退……Wi Mae Ri is the cheerful, pragmatic daughter of a failed businessman who had grown used to being constantly on the move to escape from loan-sharks. She becomes fast friends with the free-spirited indie singer Kang Moo Kyul 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, who had just returned from considerable success in the Japanese entertainment industry. Jung Suk sets up a deal with Dae Han to have Mae Ri marry his son, Jung In. Desperate to escape this predicament, Mae Ri 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.