With the outbreak of the Korean War, Su-ji and Oh-mok lose their parents. Along with their brother Su-cheol, they go live with their mother's parents. As they go to take refuge, Su-ji loses Oh-mok by accident. Time passes and with her older brother Su-cheol's success, Su-ji enters the high society. But due to the guilt of losing her younger sister Oh-mok, she does a lot of charity work constantly looking for Oh-mok. When Su-ji finally finds Oh-mok in an orphanage, she turns coldly away from Oh-mok for not having any evidence to prove that she is her sister. Oh-mok marries Il-hwan whom she has met at the orphanage and they live a hard life. Finally, Su-ji is convinced that Oh-mok is her sister but after living through such hardship, Oh-mok breathes her last.
Is Warm It Was That Winter on Netflix? Unfortunately the movie Warm It Was That Winter is not yet available on Netflix.
| Production | Kim Hwa-sik | Producer |
| Directing | Bae Chang-ho | Director |
| Writing | Park Wan-seo | Novel |
| Writing | Lee Mun-ung | Writer |
| Camera | Chung Kwang-suk | Director of Photography |
| Editing | Kim Hui-su | Editor |
| Sound | Kang Dae-sung | Sound Effects |
| Art | Kim Ho-gil | Props |
| Costume & Make-Up | Lee Hae-yoon | Costume Design |
| Costume & Make-Up | Hong Dong-eun | Makeup Artist |
| Crew | Kim Chul-suk | Special Effects |
| Art | Kim Yu-jun | Production Design |
| Sound | Kim Byeong-su | Sound Recordist |
| Production | Kim Dong-jin | Executive Producer |
| Lighting | Kim Kang-il | Lighting Director |
| Production | Kim Yeo-jin | Executive Producer |
| Sound | Jeong Min-seob | Original Music Composer |