On the review aggregator Rotten Tomatoes, the film has a 95% rating based on 87 critics, and an average rating of 7.6/10. Jang Hyuk-jin as Ki-chul, a train attendant.Sohee as Jin-hee, Yong-guk's close friend, and cheerleader.Choi Woo-shik as Yong-guk, a young baseball player.Ma Dong-seok as Sang-hwa, a tough, working-class man.

Jung Yu-mi as Seong-kyeong, Sang-hwa's pregnant wife.Kim Su-an as Su-an, Seok-woo's young daughter who wants to go to Busan to see her mother.Gong Yoo as Seok-woo, a fund manager obsessed with his work.Su-an tearfully sings the song 'Aloha ʻOe' she had wanted to perform for her father at the beginning of the film, and now sings it to honor his sacrifice. However, the soldiers then hear singing, which makes them realize the newcomers are human. Unable to see the new arrivals clearly, the soldiers at the checkpoint are instructed to shoot them. On the other side of the tunnel are soldiers stationed to defend the perimeter against zombies. Su-an and Seong-kyeong get off at Busan and begin walking through a train tunnel. As he zombifies, he thinks of the first time he held his daughter in his arms and throws himself off the locomotive with a smile. He puts Su-an and Seong-kyeong inside the engine room and shares his last words with his daughter before moving outside. Seok-woo fights him off, but is himself bitten. They encounter Yon-suk in the motorman's cab, on the verge of turning into a zombie, having been bitten when the train conductor saved him. The homeless man sacrifices himself to let Su-an and Seong-kyeong escape with Seok-woo into the train the conductor had activated. The train conductor starts a locomotive on another track but, while trying to save Yon-suk, is also killed by zombies after being pushed by Yon-suk. Heartbroken, Yong-guk stays with Jin-hee and is soon bitten by her. Yon-suk escapes after pushing the train attendant to be killed by the zombies, then does the same with Jin-hee. In the process, Seok-woo, Seong-kyeong, Su-an, and the homeless man are separated from Yong-guk and Jin-hee.

A blocked track at East Daegu train station forces the survivors to stop and search for another train.

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