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 aiming to becoming 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 secrets start being revealed one by one.