"Harlock Saga" is a six-episode OVA series that reimagines Richard Wagner's opera "Der Ring des Nibelungen" within the framework of the "Space Pirate Captain Harlock" universe. The narrative intertwines Norse mythology with science fiction, presenting a cosmic retelling of the classic tale. The story centers on the Nibelung, a powerful artifact capable of granting immense power, and the ensuing conflict over its possession.

The series begins with the Nibelung being discovered by the Nibelungen, a race of spacefaring beings. The artifact's creation by Alberich, a member of the Nibelungen, sets the stage for a struggle over its control. Alberich renounces love to forge the Nibelung, imbuing it with the power to dominate the universe. This act draws the attention of the gods, particularly Wotan, the ruler of Valhalla, who seeks to claim the Nibelung for himself. Wotan's pursuit of the artifact leads to a series of betrayals, alliances, and battles, as various factions vie for its power.

Captain Harlock, the iconic space pirate, becomes entangled in the conflict when his ship, the Arcadia, encounters the Nibelungen. Harlock's motivations are initially ambiguous, but his actions suggest a deeper connection to the artifact and its consequences. Alongside Harlock is his loyal crew, including Tochiro, the ship's engineer, and Emeraldas, a fellow pirate with her own agenda. The series explores themes of greed, power, and the cyclical nature of destruction, as the characters grapple with the Nibelung's corrupting influence.

The narrative unfolds across multiple planets and dimensions, blending mythological elements with futuristic technology. Key events include Wotan's manipulation of mortals and gods alike, the tragic fate of Siegfried, a warrior who becomes a pawn in the gods' schemes, and the ultimate confrontation over the Nibelung's fate. The series culminates in a climactic battle that underscores the futility of seeking absolute power, as the artifact's destructive potential is unleashed.

Throughout the OVA, the characters' relationships and motivations are explored, adding depth to the overarching conflict. Harlock's stoic demeanor and sense of justice contrast with the gods' ambition and Alberich's bitterness, creating a dynamic interplay of personalities. The series remains faithful to the operatic source material while infusing it with the distinct aesthetic and themes of the "Captain Harlock" franchise. The result is a unique adaptation that bridges mythology and science fiction, offering a compelling narrative within a richly detailed universe.