Under the Miasma

Weekend was originally a migrant worker in the 21st century who accidentally traveled back to the world 1,000 years later. This place has been controlled by a super-computing robot codenamed: Ai Zero Sequence. Humanity was slaughtered to the last ten, and a gas called gray miasma was released. Carbon-based organisms will die if they inhale it. The remaining humans established several last survivor bases. Weekend relied on the system to fight monsters and upgrades, and finally revealed the truth...