Baki Hanma fights a gang of 100 thugs; afterward, he is walked home by Detective Kido and his partner, who watched the fight. Baki then trains and thinks about what he should do to get stronger. Meanwhile, Kuriyagawa, the man who hired the thugs to fight Baki in order to test his strength, pays the gang's leader. Also, Baki watches a sparring match between Yuri Chakovsky, the international welterweight boxing champion, and Dinoy, Thailand's Muay Thai champion.
After returning home, Baki learns that Yuri will be fighting for the heavyweight title, so he visits Yuri at his gym. Meanwhile, Kuriyagawa tells Hanayama that he can't fight Baki until Baki has fought Yuri, but Hanayama has other plans.
After being knocked down by Baki, Hanayama flies into a rage in his office; afterward, he visits his sick mother in the hospital. Also, Baki visits Yuri in the hospital before his rematch with Hanayama.
Baki explains to his mother why he fights, visits Hanayama in the hospital, and trains. After a brief encounter with Yujiro, they decide that they will fight in one month. Baki then meets Strydum, who tells him of a mercenary group in Hokkaido, and Baki decides to go there to defeat them.
Yujiro breaks into the Prime Minister's office to prove a point; Baki fights the swordsman Kurokawa; Yujiro forces the archer Kanemoto to shoot an arrow at him; Baki visits his mother after she is rejected by Yujiro.
Anton Igari, an ex-wrestler, tells Tokugawa, an old man who runs an underground fighting circuit, about Baki and his recent global travels. In the narrative, Baki is seen training and fighting, and, while in Brazil, he visits a fighting master named Dixon. Learning of the circuit, Baki returns to Japan to meet with Tokugawa, and he fights Tokugawa's bodyguards to earn a chance to enter the circuit.
Flash forward three years: Baki is now the champion of the underground arena. Tokugawa meets with Orochi Doppo, a former champion of the arena, and asks him to enter his son Katsumi in the arena. Doppo finds Kato, a former student, at his dojo beating up his fighters, and he introduces Kato to the arena. Baki trains for a fight at the boarding house where he is staying, where Kozue, the daughter of the woman who owns the house, has a crush on him.
Kato spars with the fighters in Doppo's dojo; Kozue interferes with some bullies that are bothering Baki, which causes problems for her later; several fighters petition Tokugawa to be Baki's next opponent; Baki trains with Motobe Ito.
Yujiro shows up after Baki's fight and knocks him out, and Doppo challenges Yujiro to a fight. After watching Doppo spar with his students, Baki spars with him. Yujiro starts a fight with a group of boxers at their gym, and he fights with Motobe Izo and Baki's next opponent is revealed.