Shigeyoshi Hitotsubashi emerges as the narrative's primary antagonist. His appearance presents long silver hair veiling the right side of his face, grey eyes, and heavy silver knight armor adorned with a white fur shoulder accent, flowing into a red-and-white cape.

Twenty-one years before the central events, Shigeyoshi piloted the Onigami Takemikazuchi to annihilate the American Black Ships in Uraga Bay, halting foreign invasion and diverting Japan's history by preventing the Meiji Restoration. This cemented his status as a national hero. His personality intertwines strategic genius with merciless resolve; he delivers compelling condemnations of governmental decay yet executes adversaries without pause, exemplified by assassinating the Shogun and Minister Naosuke Ii. He perceives the ruling elite as morally degenerate and strives to dismantle their power, convinced his rebellion purifies Japan.

Shigeyoshi orchestrates a coup against the Tokugawa shogunate. After killing the Shogun, he exposes Minister Ii’s treason by invoking Takemikazuchi—the Onigami’s reaction confirming his accusations—before decapitating Ii and seizing his official seal. He occupies Edo Castle and targets Keiichiro Tokugawa, the shogunate’s heir, to eradicate resistance. Confronting Keiichiro, he proposes an alliance while deriding his competence, then assaults Nagasaki with Takemikazuchi’s energy blasts. At Shimabara Castle’s climax, he captures Kiriko Hattori, crushes her to provoke Keiichiro (though she survives), and battles Susanoo. Following defeat, he monitors Takemikazuchi’s repairs and sustains interest in Susanoo’s power.

His allies include Houkouin, sharing an ambiguously close bond, and the Shinsengumi—Isamu Kondo, Toshizo Hijikata, and Souji Okita—who enact his commands with loyalty. Another subordinate, Tsubaki, aids in covert operations. Enemies comprise Keiichiro, deemed unfit to wield Susanoo; Kiriko, exploited as bait; and Minister Ii, whose corruption he denounces publicly.

As a mecha pilot, Shigeyoshi commands Takemikazuchi with lethal mastery, deploying attacks like the purple energy blast "Heaven’s Lightning Wave" and the green energy sphere "Thunderous Lightning Bolt." His swordsmanship manifests in swift executions, notably bisecting Minister Ii.

Key quotes distill his ideology: "The dark power that boils within me shall vanquish the light" embodies his embrace of destruction, while his demand to the Shogun—"Why do you continue to let those monsters command the shogunate?"—epitomizes his crusade against corruption.