"Mobile Fighter G Gundam" is set in a future where nations have abandoned traditional warfare and instead resolve conflicts through a martial arts tournament known as the Gundam Fight. Held every four years, the tournament requires each nation to send a representative piloting a Gundam, a humanoid mecha, to compete in battles across Earth. The winner’s nation earns the right to govern the Earth Sphere until the next tournament.

The protagonist, Domon Kasshu, represents Neo Japan in the 13th Gundam Fight. Domon is a skilled martial artist driven by a personal mission: to locate his older brother, Kyoji Kasshu, who has been accused of stealing the Devil Gundam, a highly advanced and dangerous mobile fighter. The Devil Gundam possesses self-repairing and self-replicating capabilities, posing a significant threat to humanity if left unchecked. Domon’s quest is further complicated by his strained relationship with his father, Dr. Raizo Kasshu, who was imprisoned for his alleged involvement in the theft.

Throughout the tournament, Domon pilots the Shining Gundam, a mobile fighter designed for close combat, and later upgrades to the Burning Gundam. He is accompanied by Rain Mikamura, a childhood friend and mechanic who provides technical support. As Domon progresses through the Gundam Fight, he encounters a diverse array of opponents, each representing their respective nations and showcasing unique fighting styles and Gundam designs. Notable rivals include Master Asia, a legendary martial artist and former mentor to Domon, and Schwarz Bruder, a mysterious and highly skilled fighter with a personal connection to Domon.

The narrative explores themes of loyalty, redemption, and the consequences of technological advancement. As Domon uncovers the truth about the Devil Gundam and his brother’s involvement, he learns that the machine’s true purpose is to restore Earth’s environment, but its corrupted programming has turned it into a destructive force. The story culminates in a climactic battle against the Devil Gundam, with Domon and his allies striving to prevent global catastrophe.

"Mobile Fighter G Gundam" distinguishes itself within the Gundam franchise by emphasizing martial arts and personal rivalries over traditional military conflict. The series blends intense mecha battles with character-driven drama, creating a unique narrative that appeals to fans of both action and emotional storytelling.