Zatoichi is injured by a rogue samurai with a musket during his travels. He is cared for by Okuni, the daughter of Boss Bunkichi. Zatoichi arrives at Bunkichi’s and learns of an imminent conflict with rival Boss Yasugoro. Bunkichi currently owns the concessions at the ford separating the two clans, and Yasugoro desires to take it from him by any means necessary. Yasugoro continually attempts to provoke Bunkichi into a fight, but Bunkichi never lets himself be drawn into these traps. Instead, Bunkichi concentrates on throwing his annual fireworks festival for the locals.

Bunkichi’s prodigal son Seiroku returns home after a reckless time spent drinking and wasting his inheritance. Yasugoro sends some hired ronin to stir up trouble on Yasugoro’s side of the ford. When the hot-headed Seiroku confronts them, he is kidnapped and held at Yasugoro’s residence. Yasugoro lies to Bunkichi and tells him that Seiroku invaded his home and attempted to kill him, and tries to use Seiroku as bait to force Bunkichi to hand over the rights to the ford. Bunkichi refuses. Zatoichi ventures into Yasugoro’s residence and frees Seiroku. Yasugoro deduces Zatoichi’s true identity, and blackmails Bunkichi, accusing him of harboring a fugitive. Bunkichi is forced to dismiss Zatoichi from his household.

After Zatoichi departs, Yasugoro invades Bunkichi’s residence and slays him and all his men. Zatoichi, noticing that the fireworks were interrupted, turns back and discovers what has happened. He crosses back to Yasugoro’s residence and exacts revenge. He cuts down all the candles in the residence, forcing Yasugoro’s men to fight in the dark. Zatoichi easily slays all of them, and finally slays Yasugoro himself. The fireworks resume, and Zatoichi stands for a moment basking in their light.