The male protagonist Kang Joon-soo (played by Lee Seung Gi) and the female protagonist Kim Hyun Woo (played by Moon Chae Won) are childhood sweethearts who grew up together. Junsu is an elementary school teacher. He had a good impression of Xian Yu since he was a child, but was rejected by Xian Yu. After 18 years, he had been taking care of Xian Yu as a male friend, but he never dared to confess. He also fell in love with others, but it never exceeded 100 days. He always gave his girlfriend unconditionally, but he was always thrown off for various inexplicable reasons. He couldn't understand women's thoughts at all, and was judged by Hyun Woo as a man who couldn't make people's hearts. Xian Yu is a weather anchor. She is smart, lively and beautiful, and has a very high popularity among the audience. But such Hyun Woo is caught in an extramarital affair with the company's senior (played by Lee Seo Jin) and can't help herself. She drank for him and wept for him. Then call Junsu to talk about the feeling of heartache. Junsu became more and more intolerant of this situation.