Ippo Makunouchi is a very shy high school student who never had the time to make friends because he was always busy helping his mother with the family charter boat fishing business. Because he kept to himself, a group of bullies lead by Umezawa got into the habit of picking on him. On one particular day these bullies decided to give him a rather serious beating, but a middle-weight professional boxer who was passing by stopped the bullies and took the injured Ippo to the Kamogawa Gym, owned by retired boxer Genji Kamogawa, to treat his wounds. After Ippo awoke to the sounds of boxers training, the boxer who saved him, Mamoru Takamura, tried to cheer Ippo up by letting him vent his frustrations on a sandbag. It was then that they had their first glimpse into Ippo's talent for boxing. After that incident, Ippo started his regular training and began his path in Japan's professional boxing.
The story focuses heavily on character development, even during the matches something is learned about the fighters. Ippo and his friendly rivalry with Miyata is the main draw in the early part of the series. That later changes to Ippo's path towards the Japanese Featherweight Championship and eventually the world championship. Along the way we are given glimpses into the other side character's pasts, motivations, relationships to others and current boxing trials.
The anime series has two spin-off movies that were actually part of the manga. Champion Road, which takes place after Ippo becomes the Japanese Featherweight Champion and showcases his first defense of the title, and Kimura Vs. Mashiba, which pits one of Ippo's senpai (upper classmen) Kimura against the Japanese lightweight champion Mashiba (the brother of Ippo's love interest).