Futuristic post-war Japan is divided into four military zones, each commanded by opposing countries vying for total control of the country. While the Boundary War, which was fought with the assistance of humanoid mecha weaponry known as AMAIM, is long ended, the antagonism between these groups continues, and as a result, the Japanese are greatly oppressed. Amou Shiiba, a 16-year-old orphan kid surreptitiously reconstructing an abandoned AMAIM named Kenbu, comes upon Gai, an autonomous AI in need of battery power. Amou and Gai end up in the middle of a crisis because they choose to support one another, and Amou is called a terrorist and pushed out of society. Nonetheless, Amou refuses to remain silent in the face of injustice, and he starts on a journey.