Read I Have a Mansion In The Post-Apocalyptic World Manga:
Jiang Chen crossed into the judgment day after the nuclear war, and there was a mess everywhere. In order to survive, Jiang Chen led the refugees to establish a base area and set up a federation.
Then carry the judgment day’s technology and return to the true world. Change the political structure of the earth, rescue the world in a critical moment, and establish th more.. e Great Union of Earth Federation! Expanding the territory and fighting the threat from the sky.