A former Asian Games record breaker and Olympic tryout, Kim Gwang-su, endures beatings, abuse, and constant ridicule from his swimming coach. To justify this abusive behavior, his coach constantly reminded Gwang-su - this is for your own good.
| Actor | Role |
|---|---|
 Yoo Jae-sangJoon-ho | Joon-ho |
 Park Hae-joonGwang-soo | Gwang-soo |
 Lee Hang-naJung-ae | Jung-ae |
 Choi Mu-sungYoung-hoon | Young-hoon |
 Jung Ga-ramYoung Gwang-soo | Young Gwang-soo |
 Yoo Jae-myungCoach Park | Coach Park |
 Kwak Min-seokDirector Kim | Director Kim |
 Kim Do-youngRestaurant Manager | Restaurant Manager |
 Kang Ae-simHarvard Mother | Harvard Mother |
 Oh Dae-hwanWrestling Coach | Wrestling Coach |
 Kim Min-sikDetective | Detective |
 Nam Moon-chulDirector | Director |
 Cha Bo-sung1998 Player | 1998 Player |
 Lee Jung-eunOwner of Tented Restaurant | Owner of Tented Restaurant |
| JJeong Woo-geunDetective 1 | Detective 1 |