Young-ran, a bottom-of-the-table woman with a criminal record and debt, is miraculously hired as the personal bodyguard of the 70-year-old chaebol chairman, Ga Sung-ho. Entering an unfamiliar mansion, she encounters the eccentric Chairman and gradually senses a suspicious atmosphere.

Chairman Ga proposes marriage to Yeong-ran. She accepts, mortgaging her life to escape her debts. To avoid his stepdaughter, Ga Sun-young, who is after his fortune, she assumes the false identity of "Boo Se-mi" and prepares to leave for the countryside, Muchang.

Young-ran, transformed into a complete opposite of her past self, disguises herself as a kindergarten teacher, Boo Se-mi, and sets foot in Muchang for the first time. As she adjusts to the unfamiliar routine, she encounters Dong-min, who happens to pass by her at the Gahoejang mansion, and a strange tension begins to flow between them.