In the animation feature Seoul Station, the South Korean capital is besieged by the undead hordes.

What begins as a small viral outbreak becomes a catastrophe because early victims are the homeless, whose plight is ignored.

Writer-director Yeon Sang Ho, 38, says he wanted his horror movie to "mirror the society in which audiences live".

"This strongly determines how much they will enjoy the movie. It was important for me to represent characters from all walks of life," he says in an e-mail interview with The Straits Times.

Seoul Station (NC16, 92 minutes) is showing in cinemas. It is a prequel to the smash hit, the live-action thriller Train To Busan (still showing in a few cinemas), which Yeon also wrote and directed. Train To Busan has taken nearly $5 million at the box office here, making it the highest-grossing Asian film in Singapore this year.

Yeon agrees that both films are cynical about governments having the interests of citizens at heart.

"In my opinion, the onset of tragedy in a society is when the public authority abandons its people in the pursuit of power," he says.

Seoul Station is seen mostly through the eyes of the city's lowliest, such as teen runaway Hye Sun (voiced by Shim Eun Kyung) and her unemployed, videogame-addicted boyfriend, Ki Woong (Lee Joon).

As in Train To Busan, characters fend for themselves. Even the weakest among them have to become their own heroes.

Those whose job it is to protect people - the administrators, the police, the military - are busy covering up their mistakes or preoccupied with protecting property and civil order.

Hye Sun, fleeing the zombies with a group of homeless people, runs into a police station.

Instead of trusting their witness accounts, the cops scold them for their smell and move to eject them.

In Train To Busan, a railroad executive shuts others out of his protected compartment in order to save himself.

Yeon says: "It is natural to see both selfless heroes and selfish people emerge from tragic events. The selfishness of the authorities and their lack of concern for people is what I wanted to portray."

His first feature, the award-winning animated work The King Of Pigs (2011), also touches on the issue of class in South Korea and the abuse of power, as does his feature, the animated drama The Fake (2013).

Yeon's other abiding theme is the family and how fragmented the unit has become recently.

In Train To Busan, a divorced man and his daughter fight for their lives, while in Seoul Station, a teenage girl, estranged from her parents, must survive on her own.

The breakdown of society in the face of a zombie apocalypse is a reflection of the breakdown of the family, says Yeon.

Both his most recent films "allude to the end of an era" of the normal nuclear family and the rise of new ideas, he says.

"By viewing these two movies with a sense of continuity, I hope the audience will give more thought to the meaning of family and home."

Zombies are popular in pop culture now and critics have spoken about how the creatures tap current anxieties about epidemics, overcrowding and planetary resources drying up.

For Yeon, zombies are a symbol of one's "fear of society", representing "inexplicable misfortunes and misery", such as when catastrophes happen, taking lives regardless of whether the people deserve to die or not. He says: "Zombies are a representation of disasters, of becoming a victim."

• Seoul Station and Train To Busan are in cinemas.