Dr. Masahiko Mikogami established ASY and engineered its five Gousen mechs as Japan's primary defense force following the nation's military integration into the United Nations structure. He positioned ASY against the Shiromorishu, an ancient group that exerted spiritual influence over Japan for centuries, accusing them of controlling rather than guiding the nation. The Gousen mechs derived their operational power from Fairy Bones harvested from the corpse of Shikari Sennyo, a fairy formerly tied to the Shiromorishu.

Mikogami led ASY in direct assaults against the Shiromorishu, destroying their base and seemingly eliminating their successor, Tatsuya Takechi. These actions provoked a Shiromorishu campaign of vengeance. He adopted a girl named Mahoro, later revealed as Banka—Shikari Sennyo’s daughter—who infiltrated ASY under this guise, complicating his personal and strategic landscape. His history with Sogen Kasuya, the Shiromorishu’s elderly leader, fueled the core conflict between the organizations, resurfacing past events that shaped their struggle.

Mikogami maintained secrecy regarding his motivations, past actions, and the origins of the Gousen technology and Fairy Bones. This fostered distrust within ASY, particularly affecting his son Yamato, a Gousen pilot. The conflict escalated beyond ASY versus Shiromorishu when Rouran, a fairy sent to destroy the Fairy Bones, arrived. Neither faction represented unambiguous good; ASY exhibited ethically questionable traits despite its well-intentioned members. Mikogami’s legacy entwined with ancient conflicts resurrected through the misuse of Shikari Sennyo’s remains and Fairy Bones, defining the battle between ASY, the Shiromorishu, and celestial entities.