Jūrō is a yokai known as a kamaitachi, a creature often depicted as a weasel-like being with sickle-like claws. He is the middle sibling among three, with an older brother named Raishin and a younger sister named Kagari. In the traditional dynamic of a kamaitachi trio, Raishin would knock down a human, Jūrō would use his sickle to cut them, and Kagari would apply medicine to heal the wound. Originally, Jūrō was a gentle soul with a deep love for nature, and he was reluctant to harm humans. However, his family was repeatedly driven from their homes by human development and expansion. This constant displacement and loss festered within him, transforming his initial gentleness into a profound and bitter hatred for all humanity. This hatred sharpened his cutting abilities, making them stronger and more bloodthirsty than ever before.

Driven by this consuming rage, Jūrō went on violent killing sprees against humans, lashing out indiscriminately. His bloodlust became so severe that his own siblings, Raishin and Kagari, who feared the repercussions and also seemed to pity his tormented state, sought out Ushio Aotsuki, the wielder of the Beast Spear. They asked Ushio to kill their own brother, believing it was the only way to stop his rampage. During his confrontation with Ushio and the yokai Tora, Jūrō proved to be a formidable foe, his speed and power pushing both of them to their limits. In the midst of the battle, a dangerous situation arose when an explosion threatened to crush Raishin and Kagari, who were pinned down. Ushio and Tora set aside their fight to hold up a massive rock and a leaking tractor, saving Jūrō’s family from certain death.

It was this act of compassion that began to break through Jūrō’s hatred. He was moved and shocked to see a human shed tears for him and his siblings, recognizing a shared pain. Ushio recounted his own childhood memory of losing a beloved jungle gym, a small but personal loss that allowed him to relate to Jūrō’s far greater sorrow over losing his homes. After the crisis was resolved, Ushio sincerely apologized for the pain humans had caused and offered to help Jūrō and his siblings find a new, safe place to live, far from human interference. Jūrō initially seemed to accept this offer, expressing that it sounded wonderful. However, in a tragic turn, he suddenly attacked Ushio. Whether driven by an inescapable impulse of his hatred or a belief that he was beyond redemption, the action was instinctive. Ushio, reacting on instinct, struck back with the Beast Spear, fatally impaling Jūrō. As he died, Jūrō thanked Ushio for showing him kindness and compassion. He told his weeping siblings not to cry and to never lower their human disguises, for a place where yokai could live in peace, unbothered by humans, did not exist. With these final words, he passed away. Despite his tragic end, later on, in the final battle against a great evil, Jūrō reappears as a spirit to save his brother and sister from danger, showing that his love for his family endured beyond death.