In the 15th century, despite so many accomplishments he has made for the people, King Sejong, his biggest goal is still remaining; the invention of original letters that can be read and written by all the people. But courtiers who want to dominate the knowledge and the power, are against his will and discourage his belief. Frustrated King Sejong hears about a bonze Sinmi a phonogram expert, and secretly brings him in the palace.
You can now watch The King's Letters online on the following streaming providers in the United States.
| Directing | Cho Chul-hyun | Director |
| Writing | Lee Song-won | Writer |
| Writing | Geum Jung-yeon | Writer |
| Sound | Choi Tae-young | Sound Supervisor |
| Costume & Make-Up | Kim Seo-young | Makeup & Hair |
| Production | O Seung-hyeon | Executive Producer |
| Camera | Kim Tae-kyeong | Director of Photography |
| Editing | Kim Sang-bum | Editor |
| Sound | Dalpalan | Original Music Composer |
| Writing | Cho Chul-hyun | Writer |
| Production | Seong Chang-yeon | Producer |
| Costume & Make-Up | Shim Hyun-seob | Costume Design |
| Art | Ryu Seong-hie | Production Design |
| Costume & Make-Up | Lee Ji-yeon | Costume Design |
| Production | Kim Ji-hoon | Line Producer |
| Costume & Make-Up | Seo Eun-kyung | Costume Design |
| Camera | Lim Won-geun | Camera Operator |
| Directing | Kim Jun-su | Assistant Director |
| Editing | Park Jin-young | Digital Intermediate |
| Crew | Shin Young-hoon | Martial Arts Choreographer |
| Lighting | Hong Seung-chul | Lighting Director |
| Sound | Lim Hyung-geun | Production Sound Mixer |
| Art | Yoon Sung-hye | Art Direction |
| Art | Choi Ji-hye | Art Direction |
| Art | Jang Hee-sun | Art Designer |
| Camera | Jeon Young-wook | Still Photographer |
| Camera | Ji Sung-yong | Key Grip |
| Camera | No Ju-han | Still Photographer |
| Sound | Yang Hye-jin | Sound Editor |
