An older brother is a washed-up boxer. His younger brother is a genius pianist with physical disability. The brothers make up through their mother who is full of stories of her past.
Unfortunately the movie Keys to the Heart is not yet available on HBO Max.
| Crew | Ryu Seong-cheol | Stunts |
| Lighting | Kim Gyeong-seok | Lighting Director |
| Directing | Kim Deok-min | Assistant Director |
| Art | Lee Jin-hyung | Art Direction |
| Sound | Park Hyun-soo | Production Sound Mixer |
| Directing | Choi Sung-hyun | Director |
| Camera | Song Gyeong-seop | Still Photographer |
| Visual Effects | Park Eui-dong | Visual Effects |
| Production | Yeom Eun-ha | Line Producer |
| Writing | Choi Sung-hyun | Writer |
| Camera | Kim Tae-sung | Director of Photography |
| Production | Son Suk-woo | Producer |
| Production | Kil Young-min | Executive Producer |
| Production | Choi Jun-ho | Production Supervisor |
| Production | JK Youn | Executive Producer |
| Costume & Make-Up | Kim Eun-suk | Costume Design |
| Sound | Hwang Sang-jun | Original Music Composer |
| Production | Ju Seung-hwan | Producer |
| Art | Lee Tae-hoon | Production Design |
| Costume & Make-Up | Lee Jin-young | Makeup & Hair |
| Production | Jang Jin-seung | Executive Producer |
| Crew | Choi Bong-rock | Fight Choreographer |
