Jubei Yagyu emerges as a legendary swordsman enmeshed in supernatural struggles during the Tokugawa era, his origins rooted in the storied Yagyu clan. His father and grandfather, celebrated swordsmen, secured their legacy through martial prowess, with his father instructing Tokugawa shoguns. Historical ambiguity shrouds Jubei’s life, particularly a twelve-year gap fueling myths of covert missions or solitary wanderings.

Amid the Shimabara Rebellion, Jubei clashes with Amakusa Shirō, a Christian rebel leader mutated into a demonic entity by betrayal and dark forces. Commissioned by the shogunate, Jubei storms Harano Castle with ruthless efficiency, only to grapple with a moral quandary: he brokers a fragile truce, vowing to spare civilians if Shirō sacrifices himself. This pact unravels when a manipulative lieutenant falsely accuses Jubei of slaughtering children, driving Shirō to embrace a satanic rebirth.

Jubei’s blade carves through resurrected warriors and spectral adversaries, his skill etching victories against impossible odds. Though he fells Shirō in their first duel, he remains oblivious to the rebel’s resurrection via blasphemous rites. Years later, he confronts Shirō anew, now a harbinger of apocalypse marshaling undead legions. Between battles, fleeting introspection surfaces—burying fallen innocents, weighing the cost of duty—yet his resolve never wavers.

Interactions with allies and foes alike reveal a stern demeanor layered over unwavering loyalty. Fictional embellishments, like his iconic eyepatch, merge with historical threads, framing him as a relentless force against chaos. His tale intertwines with the suppression of Christianity, yet spirals into fantastical clashes with demonic pacts and unholy armies. Though the unresolved OVA curtains his journey prematurely, Jubei endures as a linchpin against annihilation, straddling the divide between rigid honor and the maelstrom of supernatural ruin.