Ichirō Miyata is a professional featherweight boxer and a central figure in the story, recognized as the primary rival of the protagonist. From a young age, Miyata was considered a prodigy, training under his father at the Kamogawa Gym. His early life was marked by a significant shift in personality; as a child he was cheerful and outgoing, but after witnessing his father's career-ending defeat and subsequent retirement, he became a calm, serious, and often stoic individual. This event became the driving force behind his boxing career, as he dedicated himself to proving that his father's style of boxing was effective on the world stage.

Miyata's motivations are deeply personal. His primary goal is to honor his father's legacy by succeeding where his father could not. This is most clearly seen when he abandons a planned match with his rival, Ippo Makunouchi, to face Randy Boy Junior, whose father was the very boxer who ended Miyata senior's career. Miyata is also characterized by a strong sense of pride and stubbornness. He refuses to move up to a more natural weight class, despite the severe physical toll his weight control exacts on his body, and he has been known to reject learning certain techniques, like uppercuts, until absolutely necessary. He holds a deep respect for his father and shares a close, supportive relationship with him, who serves as his trainer. While he has few friends outside of his former gym mates like Takamura Mamoru and Kimura Tatsuya, his bond with Ippo is the most significant relationship in his life, a mix of mutual respect and a burning desire to finally settle their score in the ring.

His role in the story is intrinsically linked to Ippo's development as a boxer. Their rivalry begins with two sparring matches at the Kamogawa Gym. Miyata won the first, but lost the second by a narrow margin, a result that has haunted both fighters. Because boxers from the same gym cannot officially fight each other, Miyata left the Kamogawa Gym to pursue a professional career elsewhere, vowing to face Ippo again in the ring. Their paths to a professional match have been repeatedly thwarted by circumstance, most notably when Miyata suffered a broken foot due to a foul by his opponent, Ryo Mashiba, during the semifinals of the East Japan Rookie King Tournament, preventing the long-awaited final bout with Ippo.

Miyata's development as a fighter is a constant process of refinement and adaptation. After his loss to Mashiba, he left Japan to train in Thailand and Korea, where he honed his signature technique, the Jolt Counter. He eventually captured the Oriental and Pacific Boxing Federation (OPBF) featherweight title, a championship his own father once held. His most personal and grueling victory came against Randy Boy Junior, where he was pushed to his limits but ultimately won using a new, unnamed technique described as "Red Lightning," signifying the emergence of his own unique boxing identity.

In terms of abilities, Miyata is an out-boxer and a counter-punching specialist. He is renowned for his extraordinary speed, precise footwork, and impeccable timing. Lacking natural knockout power in his regular punches, his main weapon is the counter, which uses an opponent's own momentum and force against them. Notable techniques include the Jolt Counter, the Cross Counter, and the dazzling Speed Hell, a blinding flurry of punches from multiple angles. He is also an excellent defensive boxer, able to memorize an opponent's attack patterns so a single punch will not work on him twice. While he fights from the outside, he is not afraid to engage in close combat if necessary, though his severe weight control leaves him with less stamina than many of his peers.