Ichi, portrayed by Jun Katsumura, is a humble yet formidable wrestling yakuza who travels on foot through a small town in search of work and fortune. Determined and skilled, he enters a local sumo match, where he faces and defeats five opponents, all of whom are sighted, showcasing his impressive strength and resilience. Despite his achievements, Ichi remains a quiet, honorable man, guided by a strong sense of justice and personal integrity.
As Ichi continues his journey, he finds himself unexpectedly attacked by Kisuke, a young yakuza with no prior connection to him. Kisuke's assault is quickly thwarted by Ichi, who easily dispatches him and confronts him about the motives behind the attack. Kisuke reveals that he was promised a reward of ten Ryō for killing Ichi, a bounty that he desperately sought to earn. Before dying, Kisuke confesses to Ichi that his mother is also a yakuza, adding layers to the young man's troubled background. However, Kisuke dies before revealing who placed the bounty on Ichi's head, leaving the true motives shrouded in mystery.
Following this confrontation, Ichi heads to the local yakuza house of the Shimonida family. Just before his arrival, the matriarch, Maki (played by [Sachiko Murase]), is with several yakuza bosses and the young heir, Sakichi (played by [junichir-narita]), during a traditional festival. Maki, a caring grandmother figure, is emotionally touched when Ichi confesses to her that he killed Kisuke in a fair fight as per the yakuza code, seeking her understanding and forgiveness. Her empathy and recognition of Ichi's honor lead her to accept his explanation, and Ichi gives her ten Ryō, claiming it was Kisuke’s wish to pass it to her.
During his stay in town, Ichi encounters Otane (Yōko Wakasugi), a woman he has loved passionately in the past and perhaps still harbors feelings for. Her life has changed since her last appearance; she is now married to a hot-tempered ronin, Tanakura (Tōru Abe). Otane confesses that she and her husband have committed many wrongdoings, revealing the troubled nature of their relationship. Meanwhile, at the inn where Ichi stays, Nobu, the innkeeper's adoptive daughter, secretly loves Sakichi, though her father, Shimazo, disapproves of their relationship.
Tensions escalate when Boss Yagiri (Yūji Hamada), a yakuza boss, perceives Sakichi as a weak leader and plans to take over his territory. Yagiri conspires with Shimazo, who is motivated by past disputes involving a gambling house owned by his family, to eliminate both Sakichi and Ichi. This plot is set against the backdrop of a traditional festival, where Yagiri’s ambitions threaten the fragile peace.
During a celebration where the yakuza bosses gather, Ichi intervenes to showcase his prowess, not just as an act of defiance but also to assert dominance and belonging. Tanakura, feeling challenged, cuts Ichi’s tea cup in half, prompting Ichi to retaliate by splitting a sake bottle while it is still being held. The display of strength establishes Tanakura as Ichi’s rival, setting the stage for a fierce confrontation.
Things take a dire turn when Sakichi informs Ichi that Tane—Otane—has been taken hostage by the yakuza. Ichi rushes to the abandoned inn, where he finds her safe and unharmed. However, the yakuza soon attack the inn, and in the chaos, a gunshot fired by one of the assailants misses. Tane tries to plead with Tanakura to spare her life, confessing her love for him and urging him to stay alive. Tragically, Tanakura, in his obsession with the bounty and his desire to eliminate Ichi, misinterprets her plea and kills her instantly by mistake.
The devastating news of Tane's death unleashes Ichi’s rage; he erupts into a merciless slaughter of the attacking yakuza, displaying his formidable combat skills. The climax culminates in a legendary duel between Ichi and Tanakura. During the fierce fight, Ichi’s sword breaks, but he cleverly stabs Tanakura with a dagger hidden in the broken sword’s handle. As Tanakura succumbs, he remarks that Ichi only had a romanticized image of Tane, implying that the ambush was her plan to secure the reward, adding a layer of tragic betrayal to the story.
The film concludes with moments of quiet reflection: Maki wishes Ichi was her son, and he, showing a rare moment of vulnerability, calls her mother. Ichi also ensures that Nobu’s hand is placed in Sakichi’s, symbolizing a connection and hope for their future. Ultimately, Ichi walks away alone once more, embodying the solitary, honorable wanderer that has defined his journey. His story is one of tragedy, loyalty, and the relentless pursuit of truth amid a world of chaos and violence.
