20-year-old repeat student Baek Choa discovers through her boyfriend’s phone that he’s been badmouthing her, saying her sex skills are terrible. Crushed with despair, she breaks up with him. Then one day, she finds out that her childhood friend and weekly tutoring partner, Lee Seunghyun, was dumped by his ex-girlfriend for the same reason. "Want to study together? Sex study!" But as the lessons go on, their original goal becomes blurry, and they start feeling drawn to each other as they meet body-to-body every week… Will they have the courage to become true lovers?