OVA
Description
Nabu Ancient hails from the planet Rinbos (alternatively called Limbos) in the M27 globular cluster, a militarized neutral zone straddling Earth Federation and Seirēn Federation space after the Milky Way Hundred Year War. Under Seirēn military occupation, Rinbos' youth endured severe hardship.

Orphaned during an assault on the Kodai Spacemen outpost on Planet Rococo seventeen years earlier, Nabu was rescued alongside infant Marcie Shima by Captain Togo Shima of the 17th Space Battleship Yamato. The Yamato later crashed on Rinbos, where Shima raised both children.

Nabu discovered a data disk in the Yamato wreckage containing schematics for the battleship and records of the Goda (or Gorda) super-ancient civilization—a technology that ignited galactic wars. Using these schematics, he spearheaded construction of the 18th generation Yamato in an abandoned Seirēn shipyard. He engineered a hybrid engine merging Earth's Wave-Motion technology with Seirēn Monopole energy to resolve power limitations, rallying fellow youths to the perilous project by staking his future on its success.

After launch, Nabu engaged in combat against Seirēn forces. When their weaponry triggered a catastrophic Monopole chain reaction destroying Rinbos, he led refugee rescues and saved his friend Aga Serene from the ruins. On Planet Rococo, he explored Goda ruins with the crew. Marcie, in a coma, interfaced with Goda datastreams, revealing the Dragon Galaxy as the civilization's origin and the original Yamato mission's likely objective—a revelation enabled by their bond.

Nabu consistently defied Seirēn authority, particularly Major Rikyard. His sibling-like connection to Marcie stemmed from their shared rescue. He protested Earth Federation attempts to commandeer the new Yamato, though the ship's systems recognized only the original crew, including him. His role expanded from escape architect to vital crewmember as the mission shifted toward uncovering Goda's origins in the Dragon Galaxy.