Yon-suk is the main antagonist of the 2016 South Korean film Train to Busan, which is considered the first zombie film made by South Korea.
Yon-suk is a rich CEO who is one of the many passengers of a train going from Seoul to Busan. Yon-suk proves to be very selfish caring only about himself and as the film progresses, he makes the zombie apocalypse worse for the film's heroes and their friends to ensure his own survival.
Yon-suk locks the door to keep out the zombies, the film's protagonist Seok-woo and his friends, family and other alive passengers from being able to enter the train box where he is. Yon-suk goes as far as to barricade the door with full effort and wrestles to keep the door closed from letting Seok-woo and his friends and family enter. Fortunately, Yon-suk loses and the heroes are able to finally enter, then Seok-woo punches Yon-suk in the face for his selfishness. Afterwards, an old lady opens the door allowing the zombies to enter in and eat up and infect everybody except Seok-woo, his daughter Su-an, a homeless man, Sang-hwa's wife Seong-kyeong, Yong-guk and his girlfriend Jin-hee, all six of whom Yon-suk banished to the next train car as he mistakenly believed the spilled blood on Seok-woo's shirt meant Seok-woo is infected.
Yon-suk and a train engineer have managed to quickly hide inside a bathroom, then they run out but with Yon-suk shoving the engineer into the zombies to save himself. Yon-suk then throws Jin-hee in front of a zombie and while Jin-hee's boyfriend is busy wrestling with the zombie, Yon-suk breaks through the glass window to board upon the new train that the conductor turns on. Seok-woo, Su-an and Seong-kyeong manage to also get on the new train, but then they see that Yon-suk is infected and is now transforming into a zombie himself. Seok-woo tells him this, much to Yon-suk's horror. Yon-suk then becomes a zombie and bites Seok-woo, before the latter throws him, and shortly later himself off the train.
- Yon-suk appears to be an analogy representing the elite rich and the first class always being prioritized over the middle and lower classes when it comes to transportation.