Ha-yoon, who has been in a short-term relationship all her life, is notified of her breakup before the 100th day by her boyfriend, Tae-ryeong, who believed it was fate. She makes one suggestion to catch him. It's a 'break-up grace period'. Tae-ryeong accepts the proposal and draws up a contract. Ha-yoon signs an unplanned new contract with Kang-jin, her best friend and college colleague, as a fake date and stimulate Tae-ryeong's jealousy, so she starts a month-long "double contract" with the two men.