Lee Jae In possesses a good appearance, he is smart and comes from a wealthy family, but he is also arrogant. His grandfather orders him to enter into a 10-month contract engagement with a female school teacher that he has never met in his life. Lee Jae In slowly falls in love with her. ~~ Based on the novel "1%ui Eoddungut" by Hyun Go Woon.

Kim Jung Hwa is a young and sincere middle school teacher, who has little interest in money. She is also extremely warm-hearted and loves to help other people. When she helps carry an elderly man's belongings from the train to another location, the elderly man is extremely thankful. This grandfather turns out to be the extremely rich owner of a well known conglomerate. His grandson, Kang Dong Won is a quick-tempered businessman who rivals his grandfather, but in an almost comical way. In an order to "tame" his favorite grandson, the grandfather agrees to give his entire fortune to the person who marries Kim Jung Hwa, therefore forcing Kang to meet the girl whom his grandfather chose. Although at first Kim and Kang don't get along because of Kang's extremely cute but bad temper, their arguments bring them closer together. Kang starts to get jealous when Kim's fellow teacher starts liking her too. Through the clever conditions that Kang's grandfather makes, Kang starts a relationship he does not look forward too. However, what looked like a relationship that would 99% not work out, turns out to be the "perfect" match, the 1% chance.