Adaptation of the short story written by Manta Aisora for the first issue of GA Bunko magazine.

The day before the ceremony marking the completion of the Yajima Stadium, Nils Nielsen invites Sei Iori, Meijin Kawaguchi, and others to an exhibition battle using the new large-scale battle system he has designed. Now that they are all reunited, Sei attempts to show off the Build Strike Cosmos that he has upgraded for the exhibition, but then he notices something missing... Meanwhile, somebody takes control of the stadium's systems, sealing Sei and the others inside. Before them appears a mysterious group, which has come to challenge them to Gunpla Battle.

Gintarou is a fox spirit that has been protecting the small Inari temple since the Edo era. Saeki Makoto's family possesses the power to see the gods' agent, but the ability is limited to one living relative at a time. When Makoto's mother passed away while she was still young, Makoto inherited the ability as the sole remaining family member. With the help of fox spirit's power, Makoto and Gintarou help the people of their community, in spite of their many differences. (Source: MangaHelpers, edited)

Corruption looms over the prosperous Russell City, where manifestations of negative emotions called Horrors cause chaos and mayhem. The Makai Order is the last bastion of hope against these unholy creatures. Using several small businesses as fronts, they deploy powerful Makai Knights and magical Makai Alchemists to combat the Horror threat. Within this secretive order, the highest rank of Golden Knight has been bestowed upon a large, powerful man named Sword, granting him use of the Garo armor and blade. He alone knows of a plot that threatens the entire Makai Order, with his only hint being the phrase “El Dorado." While fighting a Horror, he encounters Sophia "Sophie" Hennis, a teenage girl whose brother's disappearance years ago is also linked to the same phrase. The two agree to work together to uncover the truth behind "El Dorado" and the disappearance of Sophie's brother. [Written by MAL Rewrite]