In a post-war Japan with a futuristic twist, the country is divided into four military regions held by conflicting nations vying for complete control. Although the Boundary War has ended, thanks to humanoid mecha weapons dubbed AMAIM's help, the tension between the factions remains high, and the Japanese people suffer oppression. In the midst of a brewing disaster, Amou Shiiba, a 16-year-old orphan secretly rebuilding a long-abandoned AMAIM named Kenbu, comes across Gai, an autonomous AI in need of battery power. Together, Amou and Gai encounter chaos and end up labeled as terrorists, forcing Amou to go against society's rules. Despite the odds, Amou refuses to remain complacent in the face of injustice and sets out on a challenging journey packed with both hardship and camaraderie. His objective shifts from wanting a peaceful existence to freeing the Japanese population.