The story initially takes place in a futuristic dome city called Romdo, built to protect its citizens after a global environmental apocalypse. In this utopia, humans and androids (AutoReivs) coexist with each other peacefully under a total management system. Immigrants from outside of the dome are treated in harsh conditions and also by the citizens of Romdo. Lastly, there is a rule, if you ever leave Romdo, you can never go back alive.