OMG!!! This movie is a masterpiece, I have never been a fan of zombie-horror movies, although I watch them. But this Korean movie was an exception.
The character development, the love and sacrifice of a parent (from the two fathers), and the relationships between the passengers on the train (both good and bad) all make the movie an overall GOOD movie. I definitely enjoyed the acting, pacing, and texture of the story. At the end of the movie, I realized that the real villains of the story were not the zombies but the humans. The strife between them and the philosophy of individualism, that is, to fight for yourself and sacrifice others in order to survive, is what makes humans the real villains. But this clearly portrays the reality of life, where everyone only cares about themselves and struggles for their own benefit.
If you watch this movie, you are definitely going to cry for at least 30 minutes after the movie. As I am writing this, I am still crying. So if you don't enjoy movies that make you sad, then don't watch this.