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)

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.

Marquis Reinhard von Lohengramm's plot to destabilize the Free Planets Alliance succeeds when the treacherous former Rear Admiral Arthur Lynch instigates a coup on Heinessen. Equipped with a plan crafted by Reinhard himself, Lynch encourages his longtime friend Admiral Dwight Greenhill to supervise the National Salvation Military Council's toppling of the civilian government. Seeking to defend democracy and restore the Alliance constitution, Admiral Yang Wen-li faces off against his fellow citizens—and, regrettably, the father of his devoted adjutant Lieutenant Frederica Greenhill. Now with the Free Planets Alliance thoroughly occupied with their own internal matters, the forces of the Galactic Empire can safely suppress the newly formed Lippstadt League led by Duke Otto von Braunschweig. However, with his friend and loyal subordinate High Admiral Siegfried Kircheis fighting far away in the noble-controlled frontier regions, Reinhard increasingly relies on the advice of the ruthless Vice Admiral Paul von Oberstein, whose influence within the esteemed Lohengramm admiralty steadily grows. Though bloodshed is inevitable on both sides of the galaxy, Yang Wen-li of the Alliance and Reinhard von Lohengramm of the Empire each ask themselves the same questions: how will history look back on their actions? Will the ends justify the means?

Led by Reinhard von Müsel, the Galactic Empire crushes the Free Planets Alliance in the Fourth Battle of Tiamat. Arriving in the Imperial capital of Odin to a hero's welcome, Reinhard's victory earns him a promotion to High Admiral and the distinguished title of Count von Lohengramm. On the other side, Yang Wen-li safely returns to the Alliance capital of Heinessen without fanfare and reunites with his dear friends. Reinhard and Yang look forward to a long-awaited reprieve. However, at the request of the scheming Duke Otho von Braunschweig, the Imperial High Command orders the new High Admiral to invade the Alliance with a fleet of twenty thousand ships. After the Duke leaks the plan to the Alliance government, three fleets totalling forty thousand ships are sent to counter the incoming attack and recreate the famous Battle of Dagon. But even though Reinhard is outnumbered two to one, he has an ingenious plan—and Yang sees right through it. Will Yang's superiors heed his warning before it is too late?