A war that destroyed the world turned the whole world into ruins. Humanity was almost wiped out, and the surface was turned into frozen ground by the extreme weather brought about by the war. Wars lead to the emergence of various mutant creatures, abandoned and dangerous cities are no longer suitable for human habitation, and forests and grasslands have turned into boundless snow fields and ice sheets. Before the war broke out, the humans who were evacuated to the subway in time survived. Those who survived still miss the good old days, but the remnants of civilization are gradually reduced to memory. Humans who survived the subway built new homes underground. However, the strange creatures caused by the war also came to the ground along with human beings. The conflict and plunder between creatures is also repeated in a more microscopic but crueler form in the subway.