Seung Jae is a highschool student who suddenly passed away due to a traffic accident. At that time, he was dating Su Ah, a fellow student. After a year, Su Ah receives mails containing secrets surrounding Seung Jae. Turns out Seung Jae, at that time, was cheating on Su Ah and dating his friend's, Du Hyeon, sister, Eun Ho. In addition, Dong Cheol, a fellow student who aims to become a football player, quit attending his extracurricular activities after Seung Jae's death and no longer shows up at school. With the mails received, Su Ah's secrets start being revealed one by one.