Joe is the main protagonist of the Megalobox anime series, a character whose real name is never revealed. He begins the story as a man known only by his ring name, Junk Dog, an underground Megaloboxer living in the gritty outskirts of a futuristic city. Forced to throw fixed matches by his trainer and manager, Gansaku Nanbu, Joe survives on meager earnings but burns with an intense frustration and self-loathing from never fighting a real, honest bout. This life of controlled defeat fuels a destructive streak in him, often expressed through reckless motorcycle riding as an outlet for his simmering anger and desire for something more.

His entire existence is transformed after a chance encounter with Yuri, the reigning champion of Megalonia, the sport's most prestigious tournament. Yuri effortlessly defeats him, but the experience ignites a clear and unwavering motivation in Joe: to fight Yuri for real, with everything on the line. This goal becomes his singular driving force, pushing him to escape the underground and enter the professional ranks of Megalobox. To do so, he adopts the name Joe and begins fighting without any mechanical gear, a radical choice that earns him the nickname Gearless Joe. This decision is not just a gimmick but a core statement of his philosophy, as he pits his raw human power, speed, and determination against opponents enhanced by powerful exoskeleton arms.

In the first season, Joe's role is that of the ultimate underdog. He is a talented but untrained brawler whose style is a chaotic fusion of street fighting instincts and incredible resilience. He is hot-blooded, openly emotional, and lives for the thrill of a good fight. His key relationship is with Nanbu, a cynical, one-eyed coach who initially sees Joe only as a tool to make money. Over time, their dynamic evolves into a genuine, father-son-like bond built on mutual respect and sacrifice. Joe also forms a familial connection with Sachio, a young orphaned boy who becomes part of their makeshift team. His primary rivalry is with Yuri, a respectful foil who is disciplined, polished, and represents the established, corporate-backed peak of the sport. While Yuri fights with perfect, trained form and advanced gear, Joe fights with pure instinct and an unbreakable will.

Joe's character undergoes a profound and stark development, particularly when the sequel series, Megalobox 2: Nomad, is considered. After achieving his goal and becoming the Megalonia champion, a significant time skip reveals him at his lowest point. Now going by the name Nomad, Joe is a drifter haunted by trauma and guilt over Nanbu's death, addicted to painkillers, and fighting in dingy underground matches again simply to survive. His journey shifts from aspiring for glory to seeking atonement. He is a broken man running from his past, displaying a deep depression and a self-destructive, almost suicidal streak. The second season focuses on his painful path to recovery as he confronts his sins, reconciles with Sachio, and rediscovers his will to live, not just to fight. His development transforms him from a symbol of defiant ambition into a weary but wiser figure who must learn forgiveness.

Notably, Joe's most defining ability is his fighting style as a Gearless boxer. He refuses the powered exoskeleton arms that are standard in the sport, relying solely on his own body. This makes him a Badass Normal who must use blinding speed, exceptional durability, and a devastating counter-punch to overcome opponents with superhuman strength. He is a Determinator who refuses to give up, even when brutally outmatched. His signature technique involves timing a single, powerful blow while an opponent is attacking, turning their own momentum against them. This reckless, high-risk style, combined with his natural toughness and burning spirit, allows him to achieve feats that seem impossible, though it also takes a cumulative, brutal toll on his body that leads to his decline in the sequel.