Resurrected historical samurai Jubei Mitsuyoshi Yagyu, originally trained centuries prior under Musashi Miyamoto, was revived by Kumo-otoko through a foul-smelling ritual to serve Takeshi Onimaru. As one of Onimaru's key subordinates, his duty included eliminating adversaries like Yaiba Kurogane. A formidable and serious swordsman, Jubei demonstrated cunning and technical prowess in combat, famously exploiting an overextension of Kojiro Sasaki's elongated sword to defeat him in Niigata. He bears a distinctive black eyepatch over his injured left eye, spiky brown hair tied in a high ponytail, and wears a black kimono shirt beneath an orange vest, matching hakama, and traditional sandals. Challenged and defeated by Yaiba Kurogane—partly through tactical deception—Jubei recognized his former teacher Musashi Miyamoto among Yaiba's group. Overwhelmed by shame for his dishonorable actions under Onimaru and his diminished state compared to his revered past, he attempted ritual suicide via seppuku. Yaiba Kurogane and Sayaka Mine intervened, preventing his death. Consequently, Jubei defected from Onimaru's forces and joined Yaiba's team, seeking redemption and occasionally providing swordsmanship guidance to Yaiba. A significant aspect involves Jubei's involuntary transformation into the feral, antagonistic werewolf "Yajirobe" when intoxicated by alcohol. Summoned and controlled by Onimaru during these drunken states, this alter ego exhibits heightened aggression, physical agility, and bloodthirstiness. While retaining swordsmanship skills, Yajirobe becomes fiercely loyal to Onimaru, attacking Yaiba and allies without hesitation. Reversion occurs only upon unconsciousness. During the conflict against Princess Kaguya's lunar forces, Jubei sacrificed himself to facilitate Yaiba's escape, resulting in his capture. The moon general Hangetsu fused with him, compelling Jubei to fight Yaiba until accidental alcohol consumption triggered his werewolf form, allowing Hangetsu's extraction and capture. Jubei's personality combines stoicism and emotional intensity. He adheres strictly to bushido principles, reacting to perceived failures or dishonor with extreme guilt and repeated suicide attempts. He expresses discomfort with female involvement in martial matters, though treats Sayaka Mine respectfully. His drunken werewolf state contrasts sharply with his usual composure, revealing a savage, sake-loving disposition. Beyond the main series, Jubei appears in a Detective Conan crossover during the "Bear Hunters Case," where Matasaburo Saika recounts his legend, visually depicted identically to his Yaiba portrayal. His character design also inspired Kansuke Yamato in Detective Conan.