Cheong-yeon, who was introduced by a fellow bartender and ended up marrying a popular girl from Unigroup, decides to close her eyes for just a few years and live as a couple in a show window in order to pay for her mother's treatment and pay off her debts. On the day of the wedding, Do-eum, a junior who exchanged hearts in high school but turned around, reunited as a brother-in-law and brother-in-law, and suddenly Do-eum said that there was evidence of Cheong-yeon's flaws that could cancel the contract marriage... If only had known in advance that he was my brother-in-law...!'