"I can't stop thinking about you!" "I can't stop thinking about you too..." Sang Woo's daily life changes 180 degrees ever since his sister's friend Jeong Hee comes to live in their house. Every time he sees her walking around the house with wet hair and wearing just a big T-shirt, he gets erotic thoughts. He dreams of having sex with her just once until one day, he does. However, since then, Jeong Hee can't forget the night with Sang Woo and how much better he was than her fiance and starts coming back to his room...