Teenager Natsume graduates from Tanker Orphanage with dreams of becoming a Gear and fighting the Gadoll, but she is assigned to an armor repair team led by the surly leader Kaburagi. However, she discovers that he has a gentle side and is breaking the rules by keeping what appears to be a small Gadoll as a pet which she names "Pipe". One night, Kaburagi is seen removing a "chip" from a comatose man in a dark alley. While Kaburagi and Natsume are cleaning the exterior of the moving fortress city of Deca-dence, they come under attack by a horde of Gadoll, including one called a "giland" which is almost as big as Deca-dence...