"Samurai Deeper Kyo" is set in the aftermath of Japan's Sengoku period, blending historical elements with supernatural themes. The narrative centers on Kyoshiro Mibu, a seemingly mild-mannered medicine peddler who harbors a dark secret: his body is shared with the soul of Demon Eyes Kyo, a legendary and feared samurai with crimson eyes. Kyo, once a ruthless warrior, seeks to reclaim his body and exact revenge on those who betrayed him. The story begins when Kyoshiro encounters Yuya Shiina, a bounty hunter searching for Kyo to avenge her brother's death. After a confrontation, Yuya becomes entangled in Kyoshiro and Kyo's shared existence, joining them on a journey to uncover the truth behind Kyo's past and the mysterious Mibu Clan.

The Mibu Clan, a powerful and enigmatic group, plays a central role in the story. They possess advanced technology and supernatural abilities, and their influence extends across Japan. Kyo's connection to the Mibu Clan is revealed gradually, as the series delves into his origins and the events that led to his imprisonment within Kyoshiro's body. The narrative explores themes of identity, loyalty, and redemption, as Kyo struggles with his violent nature and Kyoshiro seeks to maintain control over their shared body.

Throughout the series, the protagonists encounter a diverse cast of characters, including other skilled warriors and members of the Mibu Clan. Notable figures include Benitora, a cheerful and loyal swordsman who becomes a close ally, and Akira, a young boy with a tragic past tied to the Mibu Clan. The story is driven by a series of battles, alliances, and betrayals, as Kyo and his companions confront powerful enemies and uncover the secrets of the Mibu Clan's ambitions.

The plot intertwines historical events with fantastical elements, creating a unique blend of action, drama, and mystery. The series builds toward a climactic confrontation between Kyo and the Mibu Clan, revealing the true extent of their plans and Kyo's role in their downfall. The resolution of the story addresses the fates of the main characters and the legacy of Demon Eyes Kyo, leaving a lasting impact on the world they inhabit.