Kuma is the name used for Jinnosuke, a childhood friend and fellow student of Afro Samurai who later becomes a cybernetic swordsman. His nickname, which means "bear" in Japanese, comes from the distinctive teddy bear-shaped helmet he wears, a design identical to a doll that belonged to another orphan from their shared dojo. As a youth, Jinno trained alongside Afro under the Sword Master and considered Afro his best friend and sworn brother. That bond was shattered when Afro killed their master and took the Number Two headband during the Midnight Battle Under the Bodhi Tree, an event that also claimed the lives of all the other students. Grief-stricken and badly wounded, Jinno fell from a cliff and was rescued by the scientist Dharman, who rebuilt him into the silent, emotionless cybernetic warrior known as Kuma. His body became a life-supported machine, and his voice was muted, leaving him unable to speak. Kuma wears a black keikogi and hakama with metal geta sandals and fights with a pair of katanas.

Driven by overwhelming grief and a desire for vengeance, Kuma holds Afro responsible for the massacre at the dojo. In the sequel film, he works alongside his younger sister Sio, who had been raised by foster parents, to steal the Number One headband and the jawbone of Afro's father Rokutaro from Afro's grave. Kuma and Sio intend to use forbidden science to resurrect Rokutaro as a weapon of revenge. Throughout the story, Kuma remains a stoic, seemingly emotionless enforcer who relentlessly pursues Afro. When the cloned Rokutaro is unleashed and begins choking Afro into unconsciousness, the sight of his dying former brother stirs the buried memories of their bond. Kuma breaks free of his robotic detachment and attacks the clone to save Afro, an act that leads to both him and Sio being impaled on Afro's broken sword. As Kuma dies, a spark of electricity from his cybernetic body travels through Sio's blood and revives Afro, allowing him to defeat the clone. This final sacrifice restores the familial connection Kuma once had with Afro, revealing that beneath the silent, vengeful exterior, his loyalty and love for his sworn brother never fully disappeared. Kuma's notable abilities include masterful dual-wielding swordsmanship and the enhanced strength and durability granted by his cybernetic reconstruction, though his most defining trait is the emotional and physical transformation from a loving friend into a mute instrument of revenge and finally into a redeemed brother.