주서연은 꽃미남을 싫어한다. 잘난 외모를 뽐내는 세 형제 때문에 오랫동안 시달려서인지, 서연의 이상형은 \"잘 생기지 않은 남자\"가 되었다. 그저 평범하게 살던 서연의 앞에 불청객이 나타난다. 그가 체육교사로 일하는 학교에 새로 부임한 재단 이사장, 이강우는 하루의 반을 투자해 외모를 가꿀 만큼 지독한 외모 집착증을 앓고 있다. 15년 전, 서연에게 \"뚱뚱하고 못생겼다\"라는 이유로 고백을 거절당한 후, 지독한 다이어트와 운동을 통해 꽃미남으로 거듭났다. 강우는 오랜 정신적 트라우마의 원인 제공자인 서연을 다시 만나지만, 그의 멋진 외모는 서연에게 감흥을 주지 못한다.
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.