A brief description of the I Have a Mansion In The Post-Apocalyptic World manga:
The whole world is in ruins after nuclear war. If you are lucky enough to survive on an empty planet, be prepared to face the consequences of constant radiation: constant hunger and danger, fierce zombies at night, strange mutated creatures. But for Jiang Chen, this place was heaven. Everywhere there were empty high-rises, expensive cars parked in the streets, scattered equipment and gold.