For Shion, an elite student in the technologically sophisticated city No. 6, life is carefully choreographed. School, study, and the occasional visit with his friend and classmate Safu. One fateful day, however, he takes a misstep, sheltering an injured boy his age from a typhoon. Known only as Rat, this boy is a VC—a fugitive living outside the computerized tapestry of city control—and helping him will throw Shion's life into chaos and start him down a path to discovering the appalling secrets behind the superficial perfection of No. 6.