In humanity's distant future, two interstellar states—the monarchic Galactic Empire and the democratic Free Planets Alliance—are embroiled in a never-ending war. The story focuses on the exploits of rivals Reinhard von Müsel and Yang Wen Li as they rise to power and fame in the Galactic Empire and the Free Planets Alliance.

The Free Planets Alliance counters the Galactic Imperial Navy's advance in the Astarte Starzone, still divided into the 2nd, 4th, and 6th Fleets to surround the latter on three sides. The Alliance top brass are certain that their victory is assured, but 2nd Fleet Deputy Staff Officer Commodore Yang predicts the enemy's attack on their divided forces before their encirclement is complete.

After its defeat at the Battle of Astarte, the Free Planets Alliance Navy returns to the planet Heinessen, the Alliance's capital. A memorial service is being held for the 1,500,000 Alliance soldiers who died in the battle, but according to Rear Admiral Cazerne, it's nothing but a political show put on by National Defense Committee Chairman Trunicht. Yang reluctantly attends the service, but while there, he encounters an old acquaintance he never expected to see

Sub-lieutenant Greenhill, a woman with an unusually keen memory, is added to the crew of the 13th Fleet along with several other highly well-regarded officers. Captain Schönkopf and some members of his regiment, the Rosen Ritter, board a previously captured Imperial cruiser as part of Yang's plan to infiltrate and capture Iserlohn Fortress, disguising themselves as Imperial soldiers being pursued by the Alliance

The Free Planets Alliance Navy Expeditionary Fleet encounters a grave shortage of food during its advance into Imperial territory. The 5th Fleet commander, Admiral Bewcock, conveys Yang's proposed escape plan to Supreme Commander Lobos, but Lobos fails to comprehend the situation and won't allow them to flee. Meanwhile, Reinhard has already given orders to Kircheis to strike the Alliance Navy's supply convoy. The Imperial Navy's counterattack has begun!

The Free Planets Alliance Navy Expeditionary Fleet is fighting a severe supply shortage, and the supply convoy that was sent to save them has been destroyed by Kircheis in a fierce attack. Without their desperately needed supplies, the disheartened Alliance fleet takes a hard hit from the Imperial Navy. As Reinhard's subordinates take out the Alliance fleets one by one, Yang's 13th Fleet is attacked by the Kempff Fleet.

Only a short time has passed since the Alliance's failed invasion of the Empire, and an assassination attempt on Admiral Cubersly, a key figure in the Alliance Navy, further deepens the people's anxiety. On top of that, an accidental explosion the following day takes fourteen young soldiers' lives. Growing discontent has caused revolts to break out on several planets within the Alliance. Bewcock orders Yang to put down these revolts, but before Yang has a chance to deploy, a coup d'état is executed on the capital planet Heinessen.

After defeating Legrange at the Doria Starzone, Yang's fleet heads to the capital planet Heinessen, which has been taken over by the National Salvation Military Council. Though the council's chairman, Greenhill, understands the severity of the situation, he still believes there's no way Yang's fleet can even penetrate Heinessen's gravitational field because of its specialized defense system, Artemis's Necklace. But Yang had a plan to disable Artemis's Necklace...

The battle against the Lippstadt Nobles Coalition has ended, and a victory celebration and audience with the war prisoners is being held at Geiersburg Fortress. The guards forbid Kircheis from carrying his firearm inside, even though he always had permission to keep his weapons in Reinhard's presence before. As the war prisoners face Reinhard one by one, Braunschweig's adjutant, Ansbach, enters with his leader's body in a coffin...

With their respective conflicts handily wrapped up, both Yang and Reinhard spend their time in the afterglow counting their regrets.

January 798 UC: A squadron of the Iserlohn Garrison Fleet under the command of Dusty Attenborough conducts a patrol and training mission in the Galactic Empire side of the Iserlohn Corridor, during which it encounters an Imperial patrol fleet under the command of Eihendorf. Hostilities ensue and Attenborough's squadron, largely comprised of trainees, is quickly forced into the defensive. Julian Mintz, one of the trainees, undergoes his first battle as a fighter pilot. The outmatched Attenborough Squadron is on the brink of defeat when it is saved by the entirety of the Iserlohn Garrison Fleet led by Yang Wen-li.

When the massive Geiersburg Fortress suddenly materializes in the Iserlohn Corridor, Caselnes immediately forwards a request for reinforcements to Heinessen, but now he must prepare for the imminent Imperial attack. Meanwhile, in Heinessen, Frederica is desperately looking for allies to save Yang.

The Imperial invasion force returns to the capital Odin, where Reinhard shows very different treatment to the personnel involved in the operation. Meanwhile, dissatisfaction with the new leadership is unexpectedly growing in the heart of one who was once the Empire's most loyal war hero. At Iserlohn Fortress, where peace has temporarily been restored, Yang and Julian have a very frank conversation, and Julian reveals the path he has chosen.

In a sudden public speech from Heinessen directed to all citizens, Chairman Trunicht announces that epoch-changing events are occurring as a most unexpected defector has arrived seeking protection under the ideals of freedom and democracy in the Alliance. Everyone on Iserlohn is puzzled, but Yang has a hunch that makes him feel aggravated. Then, news from Odin casts an ominous shadow across the entire galaxy.

The unexpected stalemate at the Iserlohn Corridor urges the Imperial Headquarters to muster a reinforcement fleet to be immediately sent in support of Reuenthal. Or at least this is what the Imperial crews believe... but as the fleet jumps out from subspace, it becomes clear that Iserlohn is not their destination. Then Mittermeyer, commander of the fleet, announces that they are about to turn the page in the book of history. On Fezzan, people are staring overhead with anxiety as the sky is filled with ships.