A rowdy but generous Bantamweight boxer belonging to the Tange Gym. Around 17 years old. While usually innocent and rebellious, he is more stoic than anyone and is willing to give his life for boxing. He possesses outstanding physical and mental strength and grit. He has a traditional Tokyoite spirit and is surprisingly empathetic. He considers Danpei, who saw his potential as an orphan and raised him as a boxer, to be like a father, and trusts him deeply despite their constant bickering. About two years ago, he was in a juvenile detention center for swindling money from Yoko Shiraki, where he met Kanichi Nishi and Toru Rikiishi. Currently, he has defeated the Bantamweight Rookie King Wolf Kanagushi, and his newly developed ultimate move, the "Triple Cross Counter," has been televised, making him popular with men and women across Japan.

Joe's mentor and a former boxer who acts as a father figure. President of the Tange Gym. He scouted Joe when he was an orphan years ago and, despite Joe's resistance, desperately showed his own grit to raise him into a boxer. Even when Joe was in juvenile detention, he traveled by boat to the facility to coach him fervently. Though often seen as harsh, he genuinely cares about the health and safety of Joe and Nishi. Years ago, he spent a fortune coaching an unknown boxer who eventually abandoned him; he is now betting that dream on Joe once again. Despite his suspicious appearance with an eye patch, he is actually a sensible man, and though a bit clumsy, he is very caring. As a gym executive, he possesses proper manners. He loves to drink and is a surprisingly good cook.

Joe's eternal rival, a Featherweight boxer belonging to the Shiraki Gym. Around 20 years old. He is larger than Joe (about 176cm) and always seems to be one step ahead. Mentally more mature than Joe, he has a calm and handsome personality. When he was a teenager, he was already a 6-round Welterweight boxer, but he was sent to a special juvenile detention center after jumping out of the ring to punch a spectator who had repeatedly insulted him, causing serious injury. After fighting Joe in the detention center and ending in a draw due to a cross counter, he acknowledges Joe as a true rival while still teasing him. To prepare for his match with Joe, he is seriously committed to a grueling weight reduction program at the Shiraki Gym.

Joe's partner and a large Middleweight boxer belonging to the Tange Gym. His ring name is Mammoth Nishi, and children often call him "Mammoth." He is slightly older than Joe. He used to bully Joe in the juvenile detention center, but after being broken by Joe's overwhelming strength, a sense of camaraderie developed, and he became a gentle person. He speaks with an Osaka accent. While dedicated to boxing, he is not as stoic as Joe and prefers ordinary, everyday happiness. He loves udon.

The wealthy daughter of the Shiraki Conglomerate. In the past, Joe tricked her into donating money by claiming it was for an orphanage, and a strange connection between them grew from there. Initially, Joe loathed her, telling her not to look down on the poor as a rich girl's hobby, but they gradually came to respect each other's way of life. Her grandfather, Mikinosuke Shiraki, runs the Shiraki Gym where Rikiishi belongs, and she is constantly worried about Rikiishi, who pushes himself too hard out of rivalry with Joe. She has feelings for Rikiishi but is also drawn to Joe's stubborn and honest nature. She addresses Joe as "Yabuki-kun" and Rikiishi as "Rikiishi-kun."

A Bantamweight boxer belonging to the Asia Boxing Club. Joe, fresh out of juvenile detention, picked a fight with him in the dressing room, and the resulting cross counter was picked up by the media. This forced Otaka, the president of the Asia Boxing Club, to lift the ban he had placed on the Tange Gym's professional entry using his influence. He has a stubborn and bellicose personality, but also a cowardly and petty side. He is currently recuperating after being defeated by a direct hit from the Triple Cross Counter during his fierce battle with Joe.