Jeanne Kaguya d'Arc senses the coming of the Savior-King through a divine prophecy. Led by Leonardo da Vinci, she embarks for the Star of the East. There, a young warrior named Oda Nobunaga stood in the midst of a battlefield. Powerless against the forces of a neighboring land ruled by the Takeda, Nobunaga experiences the senselessness of war and senses the dawning of a new era.

Nobunaga has a premonition that the Giant War Armor unit, The Fool, is a force heralding a new era. His confidant, Akechi Mitsuhide, is less certain, but Nobunaga only laughs off Mitsuhide's concerns.

Jeanne Kaguya d'Arc is now with the Oda clan. To attract less attention to herself as a foreigner, she disguises herself as a man named Ranmaru. Ranmaru cannot help but doubt Nobunaga due to his reckless behavior, but Nobunaga's brother, Nobukatsu, asks Ranmaru to support Nobunaga. Meanwhile, Takeda Shingen goes forth into battle in his Giant War Armor, Fuurin Kazan, in order to test Nobunaga's mettle.

Himiko of Yamatai has averted a crisis by giving Nobunaga a Regalia. However, in return, she demands that they wed. Nobunaga decides that an alliance with Yamatai will strengthen the Oda, and accepts. Meanwhile, as da Vinci plans their betrothal ceremony, Ranmaru seeks to confirm her prophecy by determining whether Nobunaga is the Savior-King.

As the inevitable clash between the Takeda and the Oda forces nears, Nobunaga and Nobuhide have a clash of their own with differences in opinion regarding tactics. Nobunaga is certain that The Fool should be taken on the offensive, and begins to rally the men. However, someone poisons him with a paralytic, and he collapses. As Nobunaga realizes the truth behind the subterfuge, Nobuhide goes forth in his own Battle Armor to duel the Fuurin Kazan...

While the Oda clan struggles with grief over an irreparable loss, Nobunaga disappears. His absence heightens the tension between Mitsuhide and the advisors.

The assassins' attacks have the Oda clan in an uproar. The advisors insist that the Takeda clan is behind the attacks, but Nobunaga decides to confirm the truth by going alone to meet Shingen...

Caesar's assault is about to upset the balance of power on the Star of the East. Nobunaga decides to regain the Regalia entrusted to him by Shingen; likewise, Caesar moves to seize the Regalia in Nobunaga's possession. As the plot thickens, Jeanne has a sinister vision...

Obtaining the Regalia of wind and light, along with Jeanne's Giant War Armor unit, has propelled the Oda clan into becoming one of the heavyweights on the Star of the East.

Giant War Armor units are en route to the trade port Takamagahara to replenish Caesar's ranks. The Oda move to requisition some of the Giant War Armor by infiltrating Takamagahara. Jeanne is grouped with Hideyoshi, who reveals a sordid past and a grudge against Nobunaga...

Mitsuhide is suspicious of Caesar's inaction. Nobunaga is certain that Caesar will strike while the Oda clan lacks experience in warfare. As predicted, Caesar launches a full-scale assault, but The Fool, Orleans, and Gokuu manage to corner the Quo Vadis.

Nobunaga responds to Caesar's demand for surrender with a tea ceremony invitation. Caesar is taken aback, but decides to go along. Ichihime is entrusted with the task of hosting the fateful wartime tea ceremony, and she firms her resolve to do everything in her power to save the Oda clan...

The unseasonal snow brings with it assassins from the West: Charlemagne and Hannibal. The Oda forces are no match for their ruthless tactics. Nobunaga is willing to risk total destruction in order to defeat them, but Jeanne bars his way, adamant that he must not become the Destroyer-King...

Nobunaga launches Azuchi on a mission to rescue Jeanne from her Round Table captors. Her abduction leads Nobunaga to acknowledge that Jeanne's power is essential to reach his goal. Meanwhile, Jeanne rejects Cesare's demand that she subjugate herself to King Arthur. Macchiavelli decides to take Jeanne to a certain location in order to inflict psychological torture...

Jeanne is finally reunited with Nobunaga, but she can't hide her doubt that Nobunaga may not be the Savior-King after all. Meanwhile, Himiko and da Vinci make a surprising discovery in the ruins of Donremy village.

Azuchi reappears in Yomotsuhirasaka after using the gate to return to the East. Himiko, severely weakened by the ordeal, tells Nobunaga about their shared history in this place. Meanwhile, the gate's reactivation galvanizes King Arthur to launch an invasion of the East by sending his most powerful general, Alexander.

Alexander and the Western army continues their inexorable advance on the Star of the East. Even Nobunaga is powerless before Alexander. His attempt to defeat Alexander by harnessing the power of numerous Regalia at great cost only serves to bring him ruin.

Defeated by Alexander, Nobunaga decides to face the dragons at Yomotsuhirasaka to obtain greater power, despite the dangers inherent in going to a realm where the dead and the living may meet. There, Nobunaga is reunited with someone he did not expect.

Alexander's invasion of the East is approaching its final stages. But as quantum pylons funnel away the ley lines' power, the Knot of Gordias is activated, which halts the flow of power in the ley lines. As Alexander moves to remedy the situation, Nobunaga, now strengthened by the dragons' power, moves to stop Alexander for good.

With the appearance of Palais Natura from the West, a clash between Nobunaga and Arthur's forces is imminent. However, Caesar makes a surprise appearance between the two camps to negotiate for peace. Seeing Nobunaga's commitment to war, Jeanne is troubled by her visions of the Destroyer-King...

Mitsuhide can no longer suppress his doubts about Nobunaga after Ichihime's death. Nobunaga also questions his own destiny, but Hideyoshi's words clear his doubts. Meanwhile, Arthur accelerates his plans for manifesting the Holy Grail and amassing the twelve Chosen.

As the Holy Grail's activation nears, Nobunaga decides to launch a frontal assault on Palais Natura with Azuchi. Hideyoshi's objection leads Nobunaga to finally realize that Himiko is at her limit. Chastened, Nobunaga decides to rely on The Fool, but Alexander bars his way. Himiko decides to take action...

Mitsuhide, now Arthur's ally, confronts Nobunaga in Palais Natura. Enraged, Nobunaga presses on through Palais Natura until Arthur finally appears. Arthur, intent on reshaping the world, gives Nobunaga a choice...