In the aftermath of the brutal suppression of the Shimabara Rebellion, the Christian rebel leader Amakusa Shirō Tokisada lies executed. But the dark sorcerer Mori Sōiken, a former retainer of a defeated lord, has perfected a forbidden ninpō technique called Makai Tenshō—the Demon Realm Reincarnation. By using a living woman as a vessel and channeling the dying will of a powerful soul, he can resurrect the dead as near-immortal, superhuman servants bound to his will. Sōiken first resurrects Amakusa Shirō and the swordsman Araki Mataemon, witnessed by the wandering swordsman Miyamoto Musashi and the strategist Yui Shōsetsu. Shōsetsu immediately pledges himself to Sōiken’s cause: the overthrow of the Tokugawa shogunate.

Over the following years, Sōiken and his growing cabal of undead masters—known as the Demon Realm Host—gather legendary figures from Japan’s martial past. Among them are the peerless duelist Miyamoto Musashi, the spear saint Hōzōin Inshun, the vengeful young master Tamiya Bōtarō, the veteran Yagyū Munenori, and the cunning Yagyū Jounsai. All are bound by their unfulfilled desires and the promise of eternal combat or glory. The shogunate’s only hope lies with the one-eyed, hot‑blooded swordsman Yagyū Jūbei Mitsuyoshi, son of the shogun’s sword instructor. The Demon Realm Host intends to make Jūbei their crown jewel, but he rejects their offer and becomes their fiercest opponent.

The story unfolds across the provinces of Kii and Yamato, centering on the domains of the Tokugawa clan and the secret fortress of the Kuki clan, who dwell in a hidden valley and practice their own forbidden arts. Jūbei, aided by a handful of loyal retainers called the Yagyū Ten People and the mysterious kunoichi Clara Oshina, fights a desperate series of duels against each resurrected master. The narrative is structured as a progression through the sacred pilgrimage sites of the Western Provinces, where each stop brings a new confrontation: Tamiya Bōtarō at Seiganto‑ji, Hōzōin Inshun at the cliffs of Sandanbeki, Yagyū Jounsai at Dōjō‑ji, and a savage clash with the false Amakusa at Kokawa‑dera. Each battle forces Jūbei to sacrifice comrades and grapple with the horror of fighting once‑honorable legends now twisted into demons.

The arc culminates in the betrayal of Musashi, who, tormented by his own legacy, seeks to prove his superiority one last time. Jūbei lures him to a small island off the coast of Kuwana—a deliberate echo of the legendary duel on Ganryūjima. There, in a rain‑swept final confrontation, Jūbei defeats the resurrected Miyamoto Musashi with a single, decisive stroke. In the aftermath, the shogunate’s agent negotiates a truce with the rebellious lord Tokugawa Yorinobu, and Sōiken’s scheme collapses. Jūbei, scarred but resolute, sails away into the east, leaving the dead to their rest.

Central characters include Yagyū Jūbei, the brash and compassionate swordsman who must fight his own father among the resurrected; Mori Sōiken, the calculating master of the dark arts; Amakusa Shirō, the charismatic yet hollow vessel of Satan’s power; Miyamoto Musashi, the proud and tragic ghost of the greatest swordsman; and Yorinobu, the ambitious daimyo who nearly plunges the realm into war. The narrative threads of loyalty, obsession, and the cost of clinging to glory weave through the violent, supernatural landscape, making this adaptation of Yamada’s classic novel a compact but vivid journey through Japan’s darkest legends.