2041, Earth. After being dragged into the planet's atmosphere, the crash of the Freeport Space Station triggers the "Great Cataclysm"—an event that ravages the Earth's environment. Reduced to a polluted wasteland, survivors wage war against each other to secure resources; ultimately, these skirmishes wipe out the entire existence of humanity. By chance, life persists on a moon base. Although ostensibly intended as an immigration outpost for a Mars exploration mission, it is quickly transformed into a city, both governing and enabling its citizens to thrive. The lunar base, officially designated "The City of Eden," embodies the hope for fully colonizing the moon. Takeru, one of Eden's many citizens in the year 2267, takes part in "Tube Races" between gangs and groups using hovercraft-like vehicles. Because he causes an accident during one of his races, Takeru is sentenced to perform volunteer work outside the city. While serving his punishment, Takeru discovers remains that might reveal the truth about Earth and Eden's origins.