Hajiki Sanada lives in Unit 74 of Night Town, a community where electricity is shut down at midnight. The world is divided into Units after resources ran out and human progress stalled several hundred years ago. Hajiki's life changes when he accidentally comes into contact with a GAD, an object that can reconstruct materials based on organic life's feelings. This encounter transforms the GAD into a massive robot, which Hajiki names Lightning, a Tekkoudo or "Iron Giant.