Train to Busan Wiki

Seong-kyeong is the tritagonist of Train to Busan.

She is protrayed by Jung Yu-mi.

Seong-kyeong is Sang-hwa's pregnant wife. With him, she goes to Busan in the same train as Seok-woo and his daughter Su-an. Being in the bathroom, she doesn't like to be disturbed by Sang-hwa who asks her how it is going.

As she leaves, she sees a passenger attacking a woman and tells Sang-hwa to stop him. The latter reveals to be infected and contaminates everyone. Sang-hwa locks him up in the bathroom and tells to his wife to run. The two run to a car where Seok-woo is and the latter closes the door on them, not wanting to let them in.

Although they enter all the same, Seong-kyeong prevents a fight between her husband and Seok-woo. She and her husband then meet Su-an. Sang-hwa asks Su-an if Seok-woo is her actual dad or not, causing Seong-kyeong to tell him nonverbally to shut up. Sang-hwa also calls Seok-woo a blood-sucker all because he's a fund manager. Seong-kyeong tells her husband not to say that stuff in front of Seok-woo's kid. Su-an says it's okay because that is what everyone says about her dad. Feeling bad for Su-an, Seong-kyeong offers her a gummy worm. She also introduces her future child while explaining that she nicknamed it "Sleepy" all because the fetus' dad is too lazy to come up with a real name for her. She then lets Su-an touch her belly.

Later, the train stops at Daejeon and Seong-kyeong goes with Sang-hwa to the station. However, the army came to protect the passengers is infected and attacks them. Seong-kyeong is separated from her husband and goes in a car with Su-an, In-gil an old lady and a homeless man. When she and the others are trapped in the toilet because of the zombies, Suan is the one who calls Sang-hwa on the phone for help and Seong-kyeong tells Sang-hwa to save them. 

The latter finds them with Seok-woo and Yong-guk a teenager. While they are all trying to get into the other passengers' cars, Sang-hwa and In-gil are infected and Seok-woo has promised to take care of Seong-kyeong for Sang-hwa. Seong-kyeong leaves with him, Yong-guk, Jin-hee, Su-an and the homeless man in the vestibule when the passengers think they are still infected. The latter are killed in turn when Jong-gil opens the door to avenge her sister In-gil. At East Daegu station, the conductor announces that he is going to change the locomotive and the group of survivors leaves the front vestibule. However, a burning train collides with another and traps Seok-woo, Seong-kyeong, Su-an and the homeless man. However, they manage to get out and the homeless man lets himself be infected to save them. The last three survivors run to the locomotive started by the conductor and find Yong-suk, infected. Seok-woo manages to knock him off the train but is bitten in the hand. He then places Seong-kyeong at the controls, places his daughter in the care of Seong-kyeong, before becoming a full fledged zombie & jumping off of the locomotive.

Soon they arrive at a tunnel, where they might have been saved. It's unknown what happened to Seong-kyeong and Su-an after, but they may have escaped thanks to the army in Peninsula. It's also not known if Seong-kyeong adopted Su-an & finally gave birth to her own child.