After the war, Japan is split into four military zones, each ruled by rival powers vying for full dominion over the nation. Although the Boundary War—waged with humanoid mecha fighters known as AMAIM—has ended, the contest among these groups continues, leaving the Japanese populace under harsh subjugation. Amou Shiiba, a 16‑year‑old orphan secretly restoring an abandoned AMAIM called Kenbu, encounters Gai, a self‑aware AI desperate for power. When they decide to aid one another, Amou and Gai become embroiled in catastrophe; Amou is branded a terrorist and ostracized. Still, he refuses to stay passive against oppression, embarking on an arduous trek filled with hardship and allies. His goal shifts from a quiet existence to freeing the Japanese people.
