Reinhard von Müsel attends a party celebrating Admiral Grimmelshausen's recent promotion. In the party, he clashes with Hermann von Luneberg and almost gets into a fistfight with him, if not for the timely intervention from Ulrich Kesler, who is appointed by Grimmelshausen to maintain the security of his residence for the party. After both Luneberg and Reinhard depart, Grimmelshausen calls for Kesler and entrusts him with a task. Siegfried Kircheis reveals to Reinhard what he found out about Elizabeth von Luneberg's former fiancé. Kaiser Friedrich IV settles on the Lohengramm countship as the one he plans to award Reinhard with. A military campaign outside the Iserlohn Corridor is announced.
Prequel to the original series, focusing on Reinhard and his steps up the chain of command in the Galactic Empire. Also focusing on the FPA's Yang Wen-li. A chronicle on how he earned the title "The Hero of El Facile" and his handling of assignments he received after the historic event. Spiral Labyrinth also continues with the background of Reinhard and Kircheis where the first Gaiden left off.
