Following the Shimabara Rebellion, Christian rebellion leader Amakusa Shiro, Kenji Sawada, is resurrected, renounces his God for abandoning him and thousands of Christians to be massacred by the Tokugawa regime, and swears vengeance. With the uncanny power to raise the dead, he tempts, resurrects, and recruits a trio of disillusioned figures to his cause as regretful demons: the betrayed samurai wife Hosokawa Gracia, Akiko Kana; the unfulfilled legendary swordsman Miyamoto Musashi, Ken Ogata; and the Buddhist monk Hozoin Inshun, Hideo Murota, who suppresses his sadistic impulses while embracing a darker, demonic role.
Yagyu Jubei, Sonny Chiba, son of Musashi's rival Tajima no Kami Munenori Yagyu, arrives at Musashi's cave to seek his teachings, only to find nothing but his former mentor’s empty armor. The encounter marks a foreboding turn as old loyalties collide with a new, malevolent force creeping across the land.
Meanwhile, Kirimaru Iga, a young Iga ninja, Hiroyuki Sanada, narrowly survives the massacre of his village at the hands of the Tokugawa-controlled Koga clan and is resurrected by Shiro’s demons for vengeance. Reborn into a world where trust is scarce, Kirimaru joins Shiro’s scheme to strike back at the Koga, even as the demons taunt Jubei during their abrupt departure.
The demons infiltrate the heart of power, spreading through Edo Castle as they manipulate events from the shadows. Hosokawa Gracia seduces Tokugawa Ietsuna, Noboru Matsuhashi, and the malevolent plot picks up speed as key figures—Izu-no-kami, Koga Genjuro, and Jubei's brother Samon—are assassinated in a chilling display of demonic influence. The ailing Tajima no Kami Munenori Yagyu, Tomisaburô Wakayama, searches for a way to stop Shiro, but dies, only to be resurrected and drawn back into the conflict as he sides with Shiro in a grim turn of fate. The episode closes with the ominous promise that the struggle between power, faith, and ferocity will only intensify.
As the story unfolds, Muramasa—the legendary exiled swordsmith—finishes a blade that Musashi once believed could cut through any obstacle. The sword, destined to play a pivotal role in the forthcoming clashes, is mourned by its creator as he sinks into exhaustion, Tetsuro Tamba breathing his last breath. In a cruel twist, the tyrannical forces demand sacrifice as the peasant uprising grows bolder: rioters are crucified, the land rebels against oppressive taxes, and the shadows of Shiro’s demons creep closer to Edo.
Kirimaru’s personal arc adds a human note to the carnage as he grapples with an emerging affection for Omitsu, a young girl touched by the turmoil surrounding the protests. Jubei, ever vigilant, tracks Muramasa for answers and learns that a sword capable of killing demons may be forged anew—a blade his ally Musashi once pursued himself in a desperate bid for strength. Muramasa, swayed by the confrontation, forges a weapon fit for Jubei’s purpose, a moment that binds fate to steel.
Shiro’s temptation intensifies as he presses Kirimaru to seduce Omitsu, a scheme Kirimaru nearly yields to before a moment of conscience arises. The witnessing Jubei spares the repentant ninja, a small mercy amid a maelstrom of vengeance and power. A lavish hunting party becomes a prelude to the larger bloodletting as the farmers’ protests erupt into full-scale defiance, illuminated by embers from a burning castle and the scheming cruelty of those who would use the chaos to bend the nation to their will.
Muramasa completes Jubei’s sword, declaring that it could even kill God, before passing away. The farmers, crucified and left to die, become symbols of the cost of rebellion, while Shiro’s crusade gathers momentum toward Edo. Kirimaru makes a last, fatal attempt to escape with Omitsu but is cut down by Shiro, a brutal reminder of the price of resistance.
In a dramatic confrontation at Funajima, Jubei challenges Musashi on the sands of memory and rivalry. The duel culminates with Jubei slaying Musashi, a moment that reshapes the balance of power as the war flows toward the capital. As the uprising presses on, Hosokawa captures Ietsuna and tears through Edo Castle with Tajima, setting the fortress alight. Shiro reveals himself to the Shogun, while Hosokawa’s reckoning ends with Ietsuna swallowed by fire and ash.
Jubei arrives, his body warded with Buddhist symbols, and faces Tajima in a brutal duel inside the burning castle. When Jubei’s blade becomes shattered, he defeats Tajima with the very Muramasa that loomed over the narrative. Shiro reappears, offering Jubei a place at his side, but Jubei refuses, severing Shiro’s head in a final blaze of righteous resolve. Even as Shiro’s body perishes, he vows to return and resurrect as long as humanity remains, retreating into the flames to fuel a legend that refuses to die.
