Texhnolyze takes place in the underground city of Lux (or "Lukuss"). The citizens of Lux have come to call it "The City" and treat it as a sentient force. Three factions vie for control of the city: the Organo, a conglomerate with ties to the criminal underworld in the prosthetics business ("Texhnolyze"); the Union, a populist group interfering with Organo's affairs; and Racan, a marauding group of Texhnolyzed youths. There is also the "Class", privileged individuals living in an adjacent sealed city, who are the intermediaries between Lux and the surface, and "Gabe", a village where the historic leaders of Lux live, worshiping Ran, a young prophetess who can see the future. The series follows Ichise, a prize fighter who loses a leg and an arm to satisfy an enraged promoter. As he struggles to accept his new robotic limbs and find a place where he belongs, he witnesses the major changes the city goes through.