During the Sengoku-era in Japan, a young boy named Kotaro flees from mysterious pursuers with his dog, Tobimaru. The monk who had been watching over Kotaro, Shouan, tells him to seek help from Master Zekkai at the Mangaku temple in Akaike Province. Meanwhile, a group of Ming foreigners under the command of the elderly Lord Bai-Luan are escorted through Akaike by local liaisons. They are ambushed by bandits, but are slaughtered by the Ming’s expert swordsman, Luo-Lang.
Kotaro and Tobimaru make their way across the land, briefly hiding out in a rundown temple where they meet No Name, a wandering swordsman. As Kotaro cooks a meal, smoke from his fire alerts his pursuers, who turn out to be the Ming foreigners accompanied by Akaike soldiers. No Name unintentionally gets involved in the fight and is able to kill the men, but Tobimaru is struck by a venomous dagger. Before No Name decides to leave, Kotaro offers to hire him as a bodyguard in order to save Tobimaru’s life and take them to their destination safely.
The trio is able to find an apothecary who is able to help Tobimaru recover over a few days. While shopping in town, No Name encounters the other Ming warriors and Luo-Lang begins to pick a fight with him for fun, but is interrupted by news of his comrade’s deaths. Upon investigation, the Ming begin to suspect the Akaike soldiers are responsible because one of the corpses was staged to appear as Tu-Si, one of the Ming warriors who previously went missing.
The Lord Akaike, who is hosting the Ming, is helping them build a large altar in exchange for large amounts of gold. It is revealed that he kidnapped the missing Ming in order to discover their true purpose for being in Japan. Under torture Tu-Si reveals that they are on a mission for the Emperor of China to find a prophesied child, Kotaro, whose blood can be drained at a certain time once a year in order to create an elixir of immortality known as the Xian Medicine. Lord Akaike changes his plans to capture the child first and hold him for a high ransom.
No Name successfully reaches the temple with Kotaro and leaves him in the care of the monks. However, it is revealed that they have already betrayed Kotaro to the Ming in order to save their own lives. A fight ensues when the Akaike also arrive to take the boy. With Lord Akaike’s treachery uncovered, the Ming take him prisoner and fortify themselves at the altar to await the prophesied time. Realizing that something went wrong, No Name goes back and frees Tobimaru, they track Kotaro and his captors. The sole remaining commander of the Akaike, Itadori, is given command of their forces by the princess and charged with rescuing the captured Lord. However, when they arrive at the fortress, Itadori seeing Lord Akaike in a compromising position, kills him and uses the opportunity to fulfill his own ambitions. The troops, now under his command, begin an assault and storm the fortress.
During the ensuing battle many of the Ming and Akaike soldiers are killed. No Name finally arrives to save Kotaro and successfully interrupts the ritual before it can be completed. Lord Bai-Luan orders the remaining Ming to capture the boy so that they may try the ritual again the next year. No Name kills two of the Ming fighters without his sword and wins the admiration of Luo-Lang, who has been searching for a worthy opponent. Luo-Lang cuts down his own benefactor, Bai-Luan, in order to save No Name from being shot. With the other Ming and Akaike forces entirely wiped out, Luo-Lang and No Name have a final duel. After sustaining many injuries No Name wins and Luo-Lang dies with shock and peace.
Kotaro and Tobimaru ride away on a horse, carrying the injured No Name to a medicine man. They talk about gathering enough money to go overseas and start a new life. As the movie ends the camera pans down on the tracks they leave in the snow and drops of fresh bleeding.