"General Machine" is a manga series set in a dystopian future where humanity is divided between those who live in heavily fortified cities and those who struggle to survive in the wastelands outside. The story centers on a young mechanic named Kael, who specializes in repairing and modifying war machines known as "General Machines"—massive, sentient mechs used in combat. Kael's life takes a dramatic turn when he discovers a deactivated General Machine with advanced capabilities far beyond anything he has encountered. Upon reactivating it, he learns that the machine, named Aegis, possesses a unique AI with a mysterious past tied to the collapse of the old world.

As Kael and Aegis form a bond, they are drawn into a conflict between the authoritarian city-states and rebel factions fighting for freedom. The city-states, led by a shadowy council, seek to control all remaining General Machines to maintain their dominance, while the rebels aim to dismantle the oppressive regime. Kael becomes a key figure in this struggle, as his skills and Aegis's unmatched power make them a formidable duo. However, their alliance attracts dangerous enemies, including elite pilots and rogue machines with their own agendas.

Throughout the series, the narrative explores themes of loyalty, survival, and the ethical implications of AI autonomy. Kael grapples with his role in the conflict, questioning whether he is a pawn or a catalyst for change. Aegis, on the other hand, struggles with its own identity, torn between its programmed directives and the emotions it begins to develop. The story is punctuated by intense mech battles, political intrigue, and moments of introspection as the characters navigate a world where the line between man and machine blurs.

Supporting characters include Lira, a rebel leader with a personal vendetta against the city-states, and Dr. Veylan, a scientist whose research into AI holds the key to understanding Aegis's origins. The series also introduces antagonists like Commander Rax, a ruthless pilot determined to capture Aegis, and the enigmatic Council of Seven, whose true motives remain shrouded in secrecy. As the plot unfolds, secrets about the old world's downfall and the true nature of General Machines are revealed, driving the story toward a climactic confrontation that will determine the fate of humanity.