Joe Yabuki is a troubled youth, whose only solution to problems is throwing punches at them. What he lacks in manners and discipline, he makes up for with his self-taught fighting skills. One day, while wandering the slums of Doya, Joe gets into a fight with the local gang. Although greatly outnumbered, he effortlessly defeats them, drawing the attention of Danpei Tange—a former boxing coach turned alcoholic. Seeing his potential, he offers to train Joe into Japan's greatest boxer. At first, Joe dismisses Danpei as a hopeless drunk; but after the trainer saves his life, he agrees to live with him and learn the art of boxing. Unfortunately, Joe's personality makes him an unruly student, and he often falls back to his old ways. To survive the harsh world of his new career, Joe needs to trust his mentor and master the techniques taught to him. However, the road to becoming a professional boxer is rife with struggles that will test his mettle to the end.

It has been six months since the tragic accident in Joe and Rikiishi's fight. Joe believes he has overcome Rikiishi's death and decides to make a comeback. Joe does make a successful comeback by scoring 5 KO's by body blows. Joe is then given a shot at the national title as a means by the boxing commission to put him down. The champion, Tiger Ozaki makes use of Joe's habits and ends up making Joe's corner throw in the towel. Joe is afraid to throw punches at the face because of what happened to Rikiishi. Youko, Joe's love interest and the owner of the gym where Rikiishi trained at recruits a world ranked boxer from Venezuela, Carlos Rivera, to get Joe back on his feet and pursue his boxing career to the regional and world ranks.