Steel runs a machine repair shop in the forest and is loved for it. His most important invention is a flexible metal called konnyaku mithril, formable into any shape or density. When someone steals both the mithril and the machine that produces it, Steel traces the theft to Dr. Bronze — a robotics authority who intends to harvest technologies from across the world for his research. Bronze's robots are already spreading everywhere. Steel sets out to dismantle them and take back what was taken.