Ha-yun's family goes bankrupt, her younger sister falls gravely ill, and her life plunges into desperation. While working a part-time job, she gets bullied and encounters Lee Jun-hyeok, a playboy chaebol heir in Seoul's high-society circle! For her sister's medical bills, Jeong Ha-yun agrees to sell her first night to Lee Jun-hyeok for 100 million won. Lee Jun-hyeok misunderstands Jeong Ha-yun as just a gold-digger selling her body, little knowing that he is the senior whom Jeong Ha-yun had a crush on since her school days! After the night, Lee Jun-hyeok still wants to use money as a transaction to keep her by his side. Unexpectedly, Jeong Ha-yun coldly states that there is only this one night. From then on, Lee Jun-hyeok suffers from unrequited love and starts a game of you run and I chase.