Seo Yeon is a temporary PE teacher in a prestigious high school called Shinhwa High School. She acts so rough and tough as if she were a boy, but she has every reason for that. Seo Yeon met her two stepbrothers and one baby brother when she was little. Unlike Seo Yeon, they had good looks, just like handsome cartoon characters. Because of her different appearance from her brothers, people didn't think of her as their sister. Therefore, she now has a phobia about handsome boys, and her ideal type of man doesn't have a good look. However, a man who has a good-looking appearance appears in front of her. 15 years ago, Kang Woo got dumped by Seo Yeon because he was ugly and fat. After getting humiliated by her, Kang Woo went abroad to study. He lost a lot of weight with a desperate effort, and now he is obsessed with his appearance. Kang Woo realizes that his trauma is related to Seo Yeon, and he wants to end this trauma. He uses his family connections to be appointed as Shinhwa High School's director. Since they have opposite personalities and appearances, there are always conflicts between them.