My Friend's Wife is a compelling drama that explores the complexities of relationships and the consequences of crossing boundaries. The story revolves around a couple who find themselves sexually dissatisfied and seek excitement by engaging in extramarital affairs. As they venture into the world of swinging and wife swapping, they discover the dangerous allure of forbidden desires and the risks involved in playing with fire.

After her mother dies, Young-jae visits her older sister's house, who took care of herself like her, and reunites with her sister, Soon-ae. She is incredibly greedy and charming. With the provocation of Soon-ae, the two develop into a secret relationship. One day when she was having a hot night with her mature lead, her daughter got stuck between the two ... A young and sexy daughter, a seasoned and mature mother, and a man wandering between mother and daughter. An unprecedented triangular romance between the three begins.