A prequel to the 2016 Korean horror movie Train to Busan, this animated movie takes place a couple of days befoee Train to Busan.
Director Yeon Sang-ho was an animation director and Train to Busan (2016) was his first live action movie. He also directed Seoul Station which was also released in 2016.

Hye-sun is a former prostitute whose current boyfriend is trying to get to go back to hooking. Hye-sun has fight and runs away.
Meanwhile a homeless person has been bitten and slowly dies on the street as everyone ignores him. The homeless person becomes a zombie and starts infecting the other homeless that live in Seoul Station.
A man claiming to be Hye-sun’s arrives and forced her boyfriend to help look for her. Hye-sun finds herself running from the growing zombie outbreak.
This is a really good prequel to Train to Busan and animation is excellent.