The 150-year-long stalemate between the two interstellar superpowers, the Galactic Empire and the Free Planets Alliance, comes to an end when a new generation of leaders arises: the idealistic military genius Reinhard von Lohengramm, and the FPA's reserved historian, Yang Wenli. While Reinhard climbs the ranks of the Empire with the aid of his childhood friend, Siegfried Kircheis, he must fight not only the war, but also the remnants of the crumbling Goldenbaum Dynasty in order to free his sister from the Kaiser and unify humanity under one genuine ruler. Meanwhile, on the other side of the galaxy, Yang—a strong supporter of democratic ideals—has to stand firm in his beliefs, despite the struggles of the FPA, and show his pupil, Julian Mintz, that autocracy is not the solution. As ideologies clash amidst the war's many casualties, the two strategic masterminds must ask themselves what the real reason behind their battle is.

After Yang Wen-li successfully captures the Iserlohn Fortress, the Free Planets Alliance grows bolder in its militaristic ambitions. With recent incursions into Galactic Empire territory and the possession of a perfect beachhead, the Alliance is now able to deal significant damage to the Empire. However, Reinhard von Lohengramm has no intention of allowing the Free Planets Alliance to gain a foothold. He is adamant about carrying on his best friend Siegfried Kircheis' dearest wish: to be the one to unite the universe. As wide-scale military clashes continue, the opportunist Adrian Rubinsky, Fezzan's ambitious leader, attempts to take advantage of the war to further his personal goals.

As Yang is ordered to appear before the Free Planet Alliance, he’s shaken by the corruption he discovers. Meanwhile, Marshal Reinhardt uncovers disloyalty under his command as an upstart admiral launches a vicious offensive to retake the Iserlohn Fortress. Struggling to make strides in this never-ending bloody war, these two finally see their true enemy lies not from without—but from within! (Source: Crunchyroll)

Ginga Eiyuu Densetsu Gaiden is the first of two OVA adaptations of side stories from the Ginga Eiyuu Densetsu novel series. This first adaptation follows the achievements of Reinhard von Müsel and Siegfried Kircheis of the Galactic Empire before the fateful Battle of Astarte. The Silver-White Valley Reinhard and Kircheis graduate from their military academy and are immediately sent to the frozen frontier planet Kapche-Lanka. Unbeknownst to them, their new superior schemes to kill Reinhard on behalf of a rival of Reinhard's sister Annerose von Grünewald. Dreams of the Morning, Songs of the Night Reinhard and Kircheis are assigned to the Imperial Military Police, where they uncover the corrupt and oppressive practices of the Empire's law enforcement. They are soon ordered to investigate the murder of a student at their alma mater. Dishonor As Reinhard awaits the bestowal of his new title of Count von Lohengramm, he sends Kircheis to the artificial resort satellite Kreuznach III for a vacation. Restless from the lack of work, Kircheis assists the local police with a drug trafficking case related to an attack on a disgraced former Vice Admiral. A Hundred Billion Stars, a Hundred Billion Lights While Reinhard is still a commodore in charge of only a single squadron, he laments the incompetence of his superiors during a battle against the Free Planets Alliance. Amassing military successes under the direct command of Vice Admiral Richard von Grimmelshausen, Reinhard repeatedly clashes with Hermann von Lüneburg, a commodore and former regimental commander of the Alliance's infamous Rosen Ritter.