The model student, Leewon has a crush on the school's most popular kid, Seo Hangeon. Leewon is happy to just watch him from afar, but when he goes up to his third year of middle school and ends up in the same class as Seohangeon, he is happy every day. Seo Hangeon is surprisingly kind, unlike the rumors, and they both gradually get closer... However, reality forces them to part, breaking their promise to stay in touch. Eight years go by. Now 28, leewon suffers from PTSD and insomnia. He returns to his hometown of Busan for graduate studies, where he reunites with Seo Hangeon..