Lonely Dad: 20s Sex Partners: Joon-gi who sends her wife and children to study abroad lives alone. But one day, he was surprised to find someone who came into his house, Mi-na. As it turns out, he got into a real estate fraud... Situation had been tight and it made her stay at home for a while. Meanwhile, her stepdaughter, Yoo-kyeong, who lives in a different house also comes home. She promises not to tell her mom that her stepfather is living with a younger woman. However, when she accidentally found her stepfather and Mi-na having sex, she feels a strange excitement...