Overview
After his mother's death, 16-year-old Hyung-joo suspects that his father is not his biological father. A secret paternity test reveals that he is not. Confused, he uses his math skills to figure out his biological father and embarks on a journey with his best friend, Jisoo, to find him.
| Actor | Age then | Age now | |
|---|---|---|---|
 | 21 | 22 | |
 | 36 | 37 | |
 | - | - | |
 | 40 | 41 | |
| - | - | |
 | - | - |