Several hundred years in the future, the Earth's resources have run exhausted, and human progress has stalled. The world has been split into "Units," and a youngster named Hajiki Sanada lives in Unit 74, in an area called "Night Town," where all power is turned off at midnight. The key to this narrative is a device known as the GAD. GADs have the capacity to rebuild materials while reacting to biological life's sensations. The size and shape of the ultimate product appear to vary according to the types of sentiments that the life carries. When Hajiki gets into contact with one by mistake, it turns into a massive robot known as a Tekkoudo, or "Iron Giant," which attacks Hajiki.