Ippo Makunouchi is a shy 16-year-old high school student who has no friends, as he spends all his free time helping his mother, who raises him alone, in the family fishing boat rental business. He is routinely bullied and humiliated by a gang of thugs led by Umezawa, one of his classmates.
One day, a professional boxer who witnessed the scene, Mamoru Takamura, rescued him from his tormentors and took Ippo to the Kamogawa Boxing Club, run by retired boxer Genji Kamogawa, for treatment. Once he is back on his feet, Ippo tries boxing following a proposal from Takamura and he proves to have an incredible strength. Takamura, amazed by the strength of the young boy, offers him to come and train in his club. Ippo discovers in him a real passion for boxing. Moreover, he is extremely happy to be at the side of Takamura whom he sees as his model. This is the beginning of a long adventure full of pitfalls for the young Ippo.