In the aftermath of the Shimabara Rebellion of 1637–1638, the Tokugawa shogunate has crushed a Christian uprising and executed its young leader, Amakusa Shirō Tokisada. Yet the story does not end with his death. An old sorcerer and ninjutsu master, Mori Sōiken, who survived the rebellion, possesses a forbidden technique called Makai Tenshō—Demon Realm Reincarnation. This art uses a woman’s body as a cocoon; a dying warrior of immense will can be reborn as a demonic being with enhanced strength and cruelty, bound to serve Sōiken’s ambition to overthrow the shogunate.

The tale begins when the strategist Yui Shōsetsu and the legendary swordsman Miyamoto Musashi stumble upon Sōiken performing the ritual to resurrect Amakusa Shirō and the killer Araki Mataemon. Shōsetsu, sharing the goal of destroying the shogunate, becomes Sōiken’s disciple. Over the following years, Sōiken, Shōsetsu, and the resurrected Amakusa gather an army of undead warriors—historical figures who died with deep regrets. Among them are the vengeful swordsman Tamiya Bōtarō, the spear master Hōzōin Inshun, the cunning Yagyū Munenori (father of the main hero), and eventually even Miyamoto Musashi himself, who is tempted by his fear of fading into obscurity.

As this army—known as the Makai Shū (Demon Realm Host)—grows and allies itself with the ambitious daimyō Tokugawa Yorinobu of the Kishū branch, they prepare to plunge Japan into chaos. Yet the most powerful potential recruit is the one-handed, one-eyed swordsman Yagyū Jūbei Mitsuyoshi, a free-spirited master of the Yagyū Shinkage-ryū. Sōiken sees Jūbei as the crown of his demon army and attempts to corrupt him through the kunoichi and agent Clara Oshina. But Jūbei, discovering the truth, breaks free of the spell and decides to oppose the invasion.

The narrative follows Jūbei as he gathers a motley band of allies—including the three courageous daughters of Kishū samurai, O-nui, O-hiro, and O-hina, and his loyal but expendable followers called the Yagyū Ten People—and moves through the landscapes of Kii Province on a pilgrimage that becomes a series of duels. Each battle is a life-or-death confrontation against a reborn legend: first Tamiya Bōtarō at the Seiganto-ji temple, then Hōzōin Inshun on the cliffs of Sandanpeki, and later Yagyū Nyūnsai (Jūbei’s own uncle) at Dōjō-ji. Jūbei is pushed to his limits, losing comrades, but also winning small victories while slowly uncovering the conspiracy behind the resurrection ritual.

Key subplots involve the tragic kunoichi Clara Oshina, who betrays Sōiken out of love for Jūbei and sacrifices herself to destroy the talisman fingers Sōiken uses for the reincarnation magic. The final arc sees Jūbei confront his own resurrected father, Yagyū Munenori, in a tense showdown at the family gravesite, and then face the resurrected Miyamoto Musashi in a climactic duel on a small island reminiscent of Ganryūjima. After defeating each demon, Jūbei must also prevent Tokugawa Yorinobu from unleashing hell upon the world.

Throughout, the manga emphasizes the horror of transformation: the once-honorable samurai become brutal monsters, and the line between humanity and demon is blurred. The story combines historical figures with supernatural action, supernatural horror, and the solitary heroism of a man who refuses to bow either to the shogunate or to the temptations of demonic power. It ends with Jūbei, exhausted but victorious, paying his respects to the fallen, while the shattered remnants of the conspiracy fade—though the scars on the land and his soul remain.