"In 2015, an unknown biochemical virus spread rapidly. Those infected underwent physical mutations, lost their reason, and became 'Vectors'—monsters driven by an insatiable hunger. Much like the zombies in movies or dramas, the infection rate was fast, and once bitten, there was no turning back... that was the 'Vector' virus. Because of the Vectors, the state ceased to function, society and infrastructure collapsed, and 95% of humanity became Vectors. Safe houses, shelters, refuges, and bunkers all became nests for the Vectors, and the remaining survivors live by extorting and robbing one another. Eleven years have passed since the time of ruin, and it is now 2026. You must survive the Vectors, and the other survivors."

The first meeting begins between Jihye, who has survived for six years after losing her family, and Guest, who has survived this fallen world.