Op de middelbare school was Choon-hwa de leidster van een hecht meidenclubje, dat destijds “Sunny” genoemd werd naar de toenmalige hit van Boney M. Jaren later ontdekt Na-mi bij toeval dat Choon-hwa terminaal ziek is. Haar laatste wens is om iedereen nog een keer te zien. Na-mi gaat op zoek naar haar vroegere vriendinnen. Het blijkt dat ze allemaal verschillend terecht zijn gekomen.
Nee, helaas is Sseo-ni nog niet beschikbaar op Netflix in Nederland.
| Crew | Hwang Jin-mo | Stunts |
| Camera | Hong Eue-su | Dolly Grip |
| Visual Effects | 백상훈 | Visual Effects Supervisor |
| Editing | 박진영 | Digital Intermediate |
| Production | 이안나 | Producer |
| Costume & Make-Up | 채경화 | Costume Design |
| Directing | Kim Jang-mi | Assistant Director |
| Camera | Woo Geum-ho | Camera Car |
| Art | Park Geun-soo | Set Decoration |
| Sound | Richard Sanderson | Songs |
| Sound | Jung Jin-wook | Production Sound Mixer |
| Production | 안병기 | Producer |
| Costume & Make-Up | Yoon Hwang-jik | Special Effects Makeup Artist |
| Sound | 김준석 | Original Music Composer |
| Visual Effects | Kim Byeong-gi | Special Effects Supervisor |
| Lighting | Lee Sung-jae | Lighting Director |
| Production | Joon H. Choi | Associate Producer |
| Production | Ahn In-ki | Producer |
| Production | Katharine Kim | Executive Producer |
| Directing | 강형철 | Director |
| Writing | 강형철 | Screenplay |
| Art | 김학현 | Set Decoration |
| Production | 유성권 | Line Producer |
| Editing | Nam Na-young | Editor |
| Camera | 이형덕 | Director of Photography |
| Sound | Lee Seung-yeop | Sound Mixer |
| Editing | Kim Mi-young | Editor |
| Writing | 이병헌 | Adaptation |
| Costume & Make-Up | Choi Hye-lim | Makeup & Hair |
| Art | Lee Yo-han | Production Design |
| Crew | Yang Gil-yeong | Fight Choreographer |
| Editing | Kim Baek-cheol | Digital Intermediate |
| Camera | 정훈 | Key Grip |
| Crew | 박근석 | Stunts |
