Complicated Cohabitation

A businesswoman who is in her thirties, Yugyeong Seo. She's in a relationship that seems to be sinking every second. One day, her younger brother's friend, Ijun Gwon, abruptly comes into her life physically and mentally, starting an odd cohabitation. Ijun Gwon, although he is the perfect house husband material, good at all kinds of house chores, he seems to dislike treating Yugyeong as a senior. Why does he care for her so much? Why does he not like to treat her as Nuna? Well, maybe this cohabitation is rather impure.