It was 2023, a time when people were living their ordinary lives.

But one day, a meteor shower fell over the United States, and monsters emerged from those meteors.

Those monsters ate humans alive or infected them, turning them into more monsters.

The entire world fell into an apocalypse, and five years have passed since then.

Now, it is 2028, in South Korea.

South Korea has long since fallen, occupied by monsters. The few remaining survivors are scattered.