Legend of the Galactic Heroes Gaiden

In July 791 UC, Reinhard von Müsel and Siegfried Kircheis, upon graduation from a military preparatory school, is posted to the planet Kapche-Lanka as their first assignment. Unbeknownst to them, Sussanna von Beenemünde, who harbours jealousy and hatred towards Reinhard's sister Annerose von Grünewald, is secretly plotting to kill him by bribing Reinhard's new superior, the base commandant of an Imperial base in Kapche-Lanka, to do so.

As a plot to kill both of them, Reinhard von Müsel and Siegfried Kircheis are dispatched by their superior to reconnoitre deep into the planet Kapche-Lanka for Free Planets Alliance activity all by themselves. Before their departure, Reinhard and Kircheis' tank is tampered with to ensure that they will not have enough fuel to make it back to base. It is nightfall before both of them realise that act and they are forced to halt and figure a way to get back to base alive. By chance, they encounter an Alliance tank advance unit and decides to ambush it for securing fuel.

Reinhard von Müsel and Siegfried Kircheis successfully ambush a Free Planets Alliance tank advance unit and secure not only fuel, but also information about an upcoming Alliance surprise attack on their base. Suspecting that their base commandant Captain Herder was responsible for their predicament, they decide to wait for any of his accomplices to appear. Eventually, Lieutenant Hugenberch finds them and after he shows hostile intent, Reinhard kills him. They then return to their base and finds the surprise attack already started. Kircheis manages to disable the attacking Alliance tanks by transmitting to them a code he wrote based on stolen data from the tanks he and Reinhard previously ambushed, enabling the Imperial forces at their base to successfully counter-attack and end the Alliance surprise attack.

Reinhard von Müsel, feigning ignorance of Captain Herder's plot to kill him, tries to convince him to attack the Free Planets Alliance base on Kapche-Lanka. Herder accepts Reinhard's suggestion, thinking it as another opportunity to kill him. As the attack plan proceeds, Herder orders Reinhard and Siegfried Kircheis on a separate assignment to isolate them. He then attempts to ambush Reinhard, but is foiled when Kircheis brings the base second in command, Commander Martel, to witness Herder's act. With his crime exposed and fearing the punishment for high treason, Herder commits suicide by leaping off a valley. Although Reinhard and Kircheis are unable to expose Sussanna von Beenemünde as the mastermind for plotting their demise, they are promoted for their contributions in the successful attack on the Alliance base and are soon transferred out of Kapche-Lanka.

In April 793 UC, Reinhard von Müsel and Siegfried Kircheis, while waiting for their next assignment, visits their alma mater in Odin. They are warmly welcomed by the students there, who respect them greatly. After observing the school for a day, Reinhard and Kircheis finally receive their new assignments in the Imperial Military Police. The next day, while browsing through the archives in the Military Police headquarters, Reinhard discovers a case handled by Ulrich Kesler during his tenure as a military police and is impressed by his unorthodox method of protecting ordinary civilians from the oppression of the Military Police. However, when he finds out that Kesler's efforts were ultimately futile, he breaks out into a rant about the degenerate state of the Galactic Empire that is only cut short by new orders from the Chief of Military Police. He and Kircheis are ordered to return to their alma mater to investigate the apparent murder of Karl von Reifeisen, a student who died the night before.

Reinhard von Müsel and Siegfried Kircheis take up lodgings in the dormitory of their alma mater for the duration of their investigation of the death of Karl von Reifeisen. During their first night, Reinhard dreams about past events of his life. The next day, Reinhard and Kircheis begin their investigation, first by examining the murder scene and then looking up on the school records of the deceased before ending with an interview with Moritz von Haase, a student sent by the school principal to assist their investigation, about the conduct and personality of the deceased for possible clues that caused his demise. Overall however, their entire day of investigation ended with no headway towards solving the case.

The first half of the episode covers Yang Wen-li's childhood, and eventual admission to the Free Planets Alliance Officer Academy on Heinessen following the death of his father. The rest of the episode covers the events of the Imperial attack on El Facil, and Yang's leadership of the civilian evacuation that earned him the title, "Hero of El Facil."

On 19 September 788 UC, Yang Wen-li is promoted to Lieutenant for his efforts in evacuating the civilians of El Facil. Six hours after his promotion, he is promoted again to Lt Commander, making it effectively a double promotion. For the next few weeks, he is thrown into a flurry of events as many people from various sectors of society ranging from the media to his estranged maternal family try to capitalise on his new fame, which he comes to detest. Eventually in October while waiting for his new assignment and avoiding the limelight, Yang is assigned by Alex Cazerne to investigate the Tuesday Correspondence and ascertain the truth behind their allegation that the Free Planets Alliance war hero Bruce Ashbey was murdered.

Yang Wen-li reviews the history of the Year 730 Mafia.

Yang Wen-li reminisces about his days in the Free Planets Alliance Officer Academy spent with Jean Robert Lapp and Jessica Edwards. He later meets with Alfred Rosas to discuss about the latter's past with the Year 730 Mafia and specifically the circumstances surrounding Bruce Ashbey's death.

The history of the Second Battle of Tiamat is chronicled. In December 745 UC, the Free Planets Alliance and the Galactic Empire clashed in the Tiamat Starzone. The Alliance Fleet under the overall command of Admiral Bruce Ashbey is composed of fleets led by members of the famed Year 730 Mafia. There are however signs of internal dissension right before the battle, threatening the morale of the fleet. In contrast, the Imperial Fleet, under the overall command of Fleet Admiral Zieten, is in high spirits, albeit being rather single-minded in hunting down Ashbey. Nevertheless, the battle starts with the Alliance fleet quickly gaining an advantage by succeeding in destroying Vice Admiral Wilhelm von Mückenberger's fleet.

The history of the Second Battle of Tiamat continues to be chronicled. On 7 December 745 UC, having temporarily retreated and regrouped, the Alliance Fleet and the Imperial Fleet engages each other again. Worsening internal conflict amongst the Alliance fleet commanders does not appear to impair their command decisions in the front lines. However, as the battle progresses into a stalemate, the Alliance Fleet is in danger of being completely surrounded by the larger Imperial Fleet. Nevertheless, the Imperial plan fails when Bruce Ashbey, having foreseen this situation, reinforces the besieged Alliance Fleet at an opportune moment, throwing the Imperial encirclement into complete disarray. He is however too late to save Vittorio di Bertini, a member of the Year 730 Mafia. As the Second Battle of Tiamat ends with a major Alliance victory, Ashbey's flagship Hard Luck is struck by stray Imperial gunfire, killing Ashbey in the process. With the end of the chronicling of the Second Battle of Tiamat, Yang Wen-li bid his farewell to Alfred Rosas and returns to his research. However, barely a day has passed when news of Rosas' sudden death is announced.