Hidetora Ichimonji, a powerful warlord, experiences a dream and decides to divide his kingdom among his three sons: Taro, Jiro, and Saburo. Taro, the eldest, will receive the prestigious First Castle and become leader of the Ichimonji clan, while Jiro and Saburo will be given the Second and Third Castles. Hidetora will retain the title of Great Lord and Jiro and Saburo are to support Taro. He shows that one arrow can easily be broken, but not three arrows together. However, Saburo smashes the three arrows across his knee and calls the lesson stupid: Hidetora foolishly expects his sons to be loyal to him, while he himself has used the most ruthless methods to attain power. Hidetora mistakes these comments for a threat; and, when his servant Tango comes to Saburo's defense, he banishes both men. Fujimaki, a warlord who had witnessed these events, and been impressed by Saburo's frankness, invites him to his dominion and offers him his daughter to marry.
Following Hidetora's abdication, Taro's wife Lady Kaede begins to urge her husband to take direct control of the Ichimonji clan. Lady Kaede plots revenge on Hidetora for treacherously massacring her family after her marriage to Taro. When Taro demands Hidetora renounce his title of Great Lord, Hidetora storms out of the castle with a few loyal retainers. He then travels to Jiro's castle, only to discover that Jiro is more interested in using Hidetora as a pawn in his own power play. Hidetora and his escort leave Jiro's castle to wander, finding no food in the villages abandoned by the peasants. Eventually Tango appears with provisions. In a moment of anger Hidetora orders his escort to burn the villages down. Tango intervenes and Hidetora learns from him of Taro's decree: death to whomever aids his father. At last perceiving his eldest sons' treachery, Hidetora takes refuge in the Third Castle, abandoned after Saburo's forces follow their lord into exile. Tango and Kyoami do not follow him.
The old Lord and his followers are attacked without warning by the combined forces of Taro and Jiro. Hidetora succumbs to madness and wanders away from the burning castle. As Taro and Jiro's forces storm the castle, Jiro's general Kurogane assassinates Taro by shooting him down in the confusion of the battle.
Hidetora is discovered wandering in the wilderness by Tango and Kyoami, who along with Saburo remain the only people still loyal to him. They take refuge in a peasant's home only to discover that the occupant is Tsurumaru, the brother of Lady Sué. Upon Jiro's return from battle, Lady Kaede blackmails him into an affair with her, and she becomes the power behind his throne. Kaede demands that Jiro kill Lady Sué and marry her instead. Jiro orders his General, Kurogane, to do the deed. Kurogane refuses, and warns Jiro that Kaede means to ruin the entire Ichimonji clan. Kurogane warns Sué and Tsurumaru to flee.
Tango rides off to bring Saburo to Hidetora. Kyoami stays to assist Hidetora, who has gone mad. In his madness, Hidetora is haunted by horrific visions of the people he destroyed in his quest for power.
Saburo's army crosses back into the Jiro's territory to find him. Jiro suspects treachery from Saburo and hastily mobilizes his army. Jiro offers Saburo a truce and Saburo accepts. Saburo learns his father's location, and takes 10 warriors to rescue him; Jiro sends a few gunners to follow Saburo, and when Hidetora has been found, to ambush them. Jiro then orders an attack on Saburo's much smaller force. In the middle of the battle a rival warlord, Ayabe, marches on Jiro's castle. Jiro's army promptly retreats back to the castle.
Saburo finds Hidetora; Hidetora recovers his sanity, and commits to repairing relationship with Saburo. However, one of the snipers Jiro had sent after Saburo's small group shoots and kills Saburo. Overcome with grief, Hidetora dies. Fujimaki and his army arrive to witness Tango and Kyoami weeping over the two. Kyoami curses the heavens for allowing Hidetora and Saburo to die, only to be told by Tango to stop, that the gods are weeping for us.
Meanwhile, Tsurumaru and Sué inadvertently leave behind the flute that Sué gave Tsurumaru years before, when he had been blinded and banished. Sué decides to return for it. Tsurumaru begs her not to go; but she insists and gives a picture of Amida Buddha to him for company during her absence. It is when she returns to Tsurumaru's hovel that she is killed by Jiro's assassin. When Kurogane hears that Lady Sué has been finally murdered by one of Jiro's men, Kurogane beheads Kaede after she admits that all along her purpose had been to exact revenge against Hidetora and his Ichmonji clan for having destroyed her family years before. Jiro, Kurogane, and all Jiro's men die in the battle with Ayabe's army that follows.
The final scene shows a funeral procession for Saburo and Hidetora. Meanwhile, blind and alone in the castle ruins, Tsurumaru accidentally drops, and loses, the Amida Buddha image Sué had given to him. The film ends with a distance shot of Tsurumaru, alone, silhouetted, atop the ruins.