By the mid-21st century, global warming had transformed Tokyo into a tropical city, and devastating squalls made civilized life there impossible. The government chose to abandon Tokyo and evacuate its residents to a massive, layered megalopolis called "Atlas." However, Atlas's limited capacity led to a surge in refugees and the rise of anti-government guerrillas. Houjyou Kuniko, the guerrilla leader, took up arms to confront the government and halt the Atlas project.