Emperor Blauné rules as the supreme leader of the Seirēn Federation, a dominant interstellar power locked in a protracted war with the Earth Federation. His reign continues after the Milky Way Hundred Year War, during which the Seirēn Federation occupies the planet Limbos. This occupation enforces severe conditions upon the populace, especially the young. Blauné's military actively seeks ancient super-civilization technology, identified through Yamato blueprints found on a data disk. This quest shatters a ceasefire and reignites the conflict with the Earth Federation.