A man and a woman realize they are separated by two years of time when they exchange letters from different years in a mailbox.
| Actor | Role |
|---|---|
 Gianna JunKim Eun-ju | Kim Eun-ju |
 Lee Jung-jaeHan Sung-hyun | Han Sung-hyun |
 Kim Mu-saengProfessor Han | Professor Han |
 Cho Seung-yeonJae-hyeok | Jae-hyeok |
| MMin Yun-jaeJeong-suk | Jeong-suk |
| KKim Ji-muJi-hun | Ji-hun |
 Choe Yun-yeongHye-won | Hye-won |
 Hong So-yeongVoice Actor | Voice Actor |
 Nam Jung-heeEun-ju's Mother | Eun-ju's Mother |
 Lee In-chulReal estate | Real estate |
| CChoi Sung-woongWorker | Worker |
| WWon Chang-yeonBungeobbang | Bungeobbang |
 Jung Suk-wonWorker | Worker |
| KKim Mi-hyeonVoice Actor | Voice Actor |
| KKwon Yeon-gyeongReal estate | Real estate |