Dark Doomsday: I Work as a Smuggler in the Wasteland

[Pure science fiction, no cultivators, golden fingers, or systems] 100 years ago, a crisis fell from the sky that wiped out half of humanity. 80 Years ago, another even more bizarre disaster followed. The earth collapsed, and a strange creature called "black liquid" occupied the entire continent. The surviving people were divided into two groups. Some stayed in the Sky City high above the sky; while the other chose to expand the city underground and coexist with the black liquid. Among the smugglers traveling between the two, a fleet named Waltz, and a mysterious girl found on the snowfield. It may become the key to the fate of the world...