A group of assassins stalks a line of blind pilgrims, scanning faces in a tense search for the famed swordsman Zatoichi, Shintarō Katsu. They stall the pursuit by presenting a few false leads and crowding the moment with taunts, but when they don’t find Ichi, they withdraw. A sly mirth breaks out among the blind men when one of them drags Ichi from cover, revealing the prank on sighted men, and Ichi simply goes on his way, choosing not to draw attention to himself.
Two kago bearers coax Ichi into carrying their load so they won’t ride without purpose. As they trundle along, a woman collapses in the road with an infant, and Ichi urges the bearers to help her, insisting she take the carriage. The assassins ambush and kill the mother, and the bearers hurry back to fetch Ichi, who accompanies them to safety just as city headmen arrive, setting the stage for a larger tragedy. In the nearby city, travel documents reveal the woman, Otoyo, was headed home to reunite with her husband, Unosuke, a silk cocoon broker, in Miyagi Village. A promissory note shows Unosuke’s debt, and it’s implied the marriage was strained, with Otoyo traveling with their baby. Feeling responsible for the woman’s death, Ichi volunteers to deliver the child to Unosuke himself, an act that binds him to a perilous mission.
The village chief assigns two villagers to accompany Ichi, and even offers a lock of Otoyo’s hair as a token of the journey. The Monju clan’s assassins keep pace, their hunger to finish what they started growing sharper. They catch up with Ichi in a town, where he openly confronts them, offering to meet for a proper fight after he delivers the infant. One attacker dies in the initial clash, but the remaining clan members withdraw, vowing that the Monju clan does not abandon a debt once it has been paid. Ichi returns to find his temporary companions flinch and flee, yet his resolve remains steady as the pursuit continues.
On the road, the Monju faction allies with Hangoro, a boss who agrees to join the hunt. The two groups press forward in concert, determined to reclaim the baby. In a roadside confrontation, Ichi is changing the child’s diaper when the assailants close in; the fight erupts, and Ichi defends himself with lethal skill, killing several before the remaining Monju men retreat. The threat to the child intensifies, but Ichi’s focus steadies as he refuses to let fear interrupt his duty.
To tend to the infant’s needs, Ichi gambles for money to buy softer diapers and, after earning a substantial win, tethers the baby’s sleep with quiet, deliberate care. A casino boss tries to rig a one-on-one game in a bid to destabilize Ichi, but the gambler’s luck returns the odds, and Ichi’s calm hands seal a generous win. His victory prompts a pursuit by the boss’s men, who are silenced with a discreet, shushing command so the child can stay asleep.
That night, Ichi hires a working woman to watch the baby while he rests. She finds the arrangement unusual but agrees, acknowledging the unusual ease of caring for the child for once. The next day, a clever woman thief, Ikuko Mōri as Oko, schemes to use Ichi as cover to rob a victim. Ichi plays along, even posing as the thief’s husband and displaying skilled swordcraft to deter the rightful victim. Oko, impressed by the money Ichi carries, offers to stay and help watch the baby, and he reluctantly hires her when they talk through the risks and responsibilities.
At the inn, the blind pilgrimage is briefly seen passing through as Ichi’s party checks in. Oko’s restless attentions spark friction: she steals a nightingale whistle, which Ichi gently calls her out for, and she leaves in a huff. He makes amends with the infant by protecting him, and when Oko inadvertently causes a small disruption by splashing the child, Ichi steers the situation with care. While watching from the sidelines, one assassin tries to reclaim a weapon Ichi had dropped, but a hand-to-hand struggle unfolds, and Ichi’s swift defense thins the ranks, with the leashed combat allowing him to reclaim his sword and dispatch three more attackers. Waheiji, the clan’s leader, slips away into the night.
A moment on the road signals a turning point as the woman vows to abandon stealing; the trio continues toward Miyagi Village. Upon arrival, the woman is reluctant to surrender the baby, but Ichi remains firm that the child must be given up that day, as to avoid dragging the infant into an endless cycle of danger. The woman hopes to stay with Ichi, yet he pays her and sends her away to begin a new life. He carries the child to Unosuke’s house, where the documents and the truth of their past are laid bare: Unosuke tears up the papers and denies any marriage, accusing Ichi of pressing him for support. He insists he plans to marry the daughter of a local boss instead, and Ichi realizes that the controlled deception is a trap. He decides to take the baby rather than allow the man to sever the family’s bond.
Outside, Waheiji lurks, waiting for the inevitable confrontation, while Oko discovers Ichi still cradling the infant and ponders their future together. He reveals that Unosuke’s plan to cast off his wife was a weapon, a cruel ruse to rid himself of the burden. Oko’s feelings shift; she hopes for a future with Ichi, but he urges her to stop following him and to seek her own path.
Inside Unosuke’s house, Waheiji presses Unosuke for help, hoping to leverage Ichi’s weakness for his own rise. But a turn toward the temple arises when Ichi, in need of a safe harbor, faces a monk who urges confinement of the child for the boy’s best interests. The monk contends that Ichi’s yakuza past and drifting life would doom the child, and suggests the temple might shelter him. When Unosuke’s men threaten the temple, Ichi reluctantly relinquishes the child to the temple, intending to face his pursuers in the woods, trusting the monk’s protection.
Torches flare as the pursuers close in, the air crackling with the scent of fire. Ichi fights through the ambush, his body marked by flames he quickly rolls to extinguish. Waheiji presses the assault, but Ichi slays the attacker and calls Unosuke’s name, forcing a final confession: Unosuke had lied, promising to raise the child, but now must confront his own choices. In a last, brutal twist, Unosuke lunges for Ichi’s sword and is killed in the struggle, leaving the fate of the child ambiguous but clear in Ichi’s dispassionate resolve.
With the infant left safe at the temple, the blind pilgrimage passes by once more as Ichi continues on his solitary route. The village, the temple, and the road fade into the distance, and the lone swordsman strides forward, forever defined by a life spent balancing mercy and danger, duty and freedom.
