In ancient times, the moon god Tsukiyomi [link to actor] transforms out of jealousy toward his sister, the sun goddess Amaterasu, and becomes the eight‑headed serpent Orochi with a plan to wipe out the Earth. The sea god Susanoo defeats Orochi and seals Tsukiyomi’s power inside the enchanted Sword of Dark Clouds, a blade that holds the god’s might. Fearing the danger of Tsukiyomi breaking free, Tsukiyomi’s father, Izanagi, seals him away in an icy prison and casts him far from the world.
Several years pass, and Emperor Keiko of Yamato grows to loath his twin son, Oousu, whom a cruel premonition haunts. Keiko enlists a mysterious shaman, Tsukinowa, to kill Oousu, but Amano Shiratori—the phoenix and the White Bird of the Heavens—intervenes and thwarts the plan. Keiko’s sister interprets the event as divine sign and chooses to raise Oousu herself, setting the stage for a remarkable destiny.
Ten years later, Oousu is subtly steered from a cave by his aunt’s guardians, Genbu and Seiryu, and a chance encounter changes his fate. At night, he discovers a strange comma‑shaped gemstone that whisks him to a mysterious realm. There, the mystic King Bullhead prophesies that Oousu will become a warrior of the gods once he gathers three lights. As Oousu grows into a young man, he earns a pardon from Keiko and returns to the castle, only to be struck by tragedy when his mother, Empress Inahi, dies of a mysterious illness. In a defensive clash with his brother, Oousu unintentionally kills him with the very gemstone that led him on this path.
Keiko, furious at the bloodshed, banishes Oousu from the palace and charges him with the duty of subduing the barbarians of the Kumaso domain. On his way, he stops at a shrine and meets a steadfast priestess, Oto Tachibana, who joins him on a perilous journey. Together with Genbu and Seiryu, they raid the royal fortress, killing the usurper King Kumaso Takeru, who attempted to sacrifice Oto to the god Kumasogami. Ousu frees Oto and receives the sacred shrine mirror from Amano, a guardian of the realm.
This victory earns Ousu the title Yamato Takeru, yet Keiko remains unconvinced of his worth. An ominous warning from his aunt reveals that Tsukiyomi’s return could threaten Earth itself. She urges him to safeguard the Sword of Dark Clouds with utmost care. Naively, Ousu retrieves the blade, only to be duped by Tsukinowa, who calls forth Kaishin Muba, disguised as Inahi, and exposes himself as one of Tsukuyomi’s fangs. Ousu, enraged, wounds Tsukinowa in retaliation and loses the sword, which restores Tsukiyomi to full power. Tsukinowa dies, his identity as a treacherous agent revealed.
As a solar eclipse drenches the world in shadow, Tsukiyomi reclaims the Sword of Dark Clouds, and the land spirals into chaos. King Bullhead, revealed to be Susanoo, guides Ousu toward the truth: his destiny will require a power that can truly end Tsukiyomi. Susanoo tests Ousu with the blade Sword of Karasai, pulled from a stone—the only weapon capable of killing Tsukiyomi. With Oto Tachibana by his side, Ousu and Oto are transported to the Moon to confront Tsukiyomi, who reverts into Orochi for a final showdown. Amano lends aid, launching an aerial strike against Orochi, but the two heroes are overwhelmed.
In a heartfelt sacrifice, Oto gives her life energy to sustain Ousu. He realizes Susanoo’s prophecy is coming true: he now bears the shrine mirror, wields the Sword of Karasai, and carries Oto’s spirit within him. Ousu transforms into the mighty warrior Utsuno Ikusagami and defeats Orochi, which then reverts to Tsukiyomi. With Tsukiyomi defeated, Oto returns to life, and Susanoo instructs Ousu, telepathically, to seal Tsukiyomi’s spirit inside a gemstone and cast it into outer space, ending the eclipse and restoring sunlight to the world.
As Amano carries them home to Earth, Keiko still longs to see Ousu. Reluctantly, Ousu and Oto part ways at Yamato, and the Sword of Dark Clouds is returned to its homeland, marking the end of one epic odyssey and the dawn of another.
