Baek Cho-ah, a 20-year-old repeat student, discovers on her boyfriend’s phone that he has been badmouthing her sexual skills, saying they’re terrible. Overcome with deep despair, she decides to break up with him. One day, she learns that Lee Seung-hyun, her childhood friend who tutors her every week, also broke up with his ex-girlfriend for the same reason. “How about we study together? Let’s study sex!” However, as the lessons continue, their original goal starts to blur, and little by little they begin to feel attracted to each other as they get physically closer every week. Will they be able to gather the courage to become true lovers?