Yumi is a 30-year old, ordinary woman who struggles with expressing her feelings. Told from the perspective of the many brain cells in her head, she experiences growth in both her love life, her career, and finds happiness in the small joys of everyday life.
| Actor | Role |
|---|---|
 Kim Go-eunKim Yu-mi | Kim Yu-mi |
 Kim Jae-wonShin Soon-rok | Shin Soon-rok |
 Jun Seok-hoAhn Dae-yong | Ahn Dae-yong |
 Lee Yu-biLee Ruby | Lee Ruby |
 Mi RamKang Yi-da | Kang Yi-da |
 Choi DanielKim Ju-ho | Kim Ju-ho |
 Cho Hye-jeongBaek Na-hee | Baek Na-hee |
 Sung Ji-ruKim Man-Sik | Kim Man-Sik |
 Park Se-inProducer Jang | Producer Jang |