[Info]
[Plot]
On a live music radio show, a letter arrives from the 23 years in the past. Through the letter, the first love and friendships of five friends are revealed.
[Cast]
 |
 |
 |
 |
 |
| Do Kyung-Soo | Kim So-Hyun | Yeon Jun-Suk | David Lee | Joo Da-Young |
| Bum-Sil | Soo-Ok | San-Dol | Gae-Duk | Gil-Ja |
 |
 |
 |
 |
 |
| Park Hae-Joon | Kim Ji-Ho | Park Yong-Woo | Lee Dae-Yeon | Hwang Suk-Jung |
| Min-Ho | Gil-Ja (adult) | Hyung-Joon | Soo-Ok’s father | Gae-Duk’s mother |
 |
 |
| Park Jung-Min | Lee Beom-Soo |
| Yong-Soo | Yong-Chul |
