With his father away, Ippo Makunouchi assists his mother in managing their family's fishing boat business. Due to his timid nature, perpetual fatigue, and the lingering scent of the ocean, he frequently becomes a target for local bullies who beat him up. One day, the renowned boxer Mamoru Takamura intervenes during an assault and brings Ippo to the Kamogawa Boxing Gym to recuperate. There, Takamura and his teammates, Masaru Aoki and Tatsuya Kimura, are stunned by Ippo's powerful punches, a strength honed through years of labor at the fishery.
Following a brief training stint with Takamura, Ippo reveals his potential in a sparring session against the boxing prodigy Ichirou Miyata. This encounter establishes Miyata as a rival and Genji Kamogawa, the gym's owner and former boxer, as a mentor. As Ippo embarks on his journey toward a professional boxing career, he encounters increasingly formidable opponents. Through victories, defeats, and relentless training, Ippo strives to realize his dream of greatness. His robust physique and indomitable fighting spirit fuel this young boxer's resolve to surmount the obstacles that lie ahead.