Magomura Kanbei is a central character in the film Lone Wolf and Cub: Baby Cart to Hades, serving as a tragic foil to the protagonist, Ogami Itto. Kanbei is a ronin, a masterless samurai, who once held a prestigious position as the Chief Palanquin Guard for the Maruoka Clan. He is a skilled and principled warrior, yet he finds himself wandering as a mercenary, having been stripped of his status and honor.

The source of Kanbei’s disgrace is the core of his character and motivation. In a flashback, it is revealed that while escorting his lord, the party was ambushed. Kanbei, assessing the dire situation, made a tactical decision to leave his post and charge ahead to single-handedly kill the attacking force, an act that successfully saved his master's life. However, this action was deemed undutiful and unworthy of a warrior by the strict, unchanging code of bushido. For committing an act of initiative that broke formation, he was expelled from the clan. This profound injustice has left him a broken and disillusioned man, wandering the countryside with what appears to be a death wish, seeking a way to reconcile his practical heroism with the rigid rules that condemned him.

In the story, Kanbei is first encountered as part of a group of three other rough watari-kashi, or hired swords for hire. He stands apart from them, still clinging to the old ideals of bushido while his companions have abandoned all pretense of honor. This contrast is made brutally clear when the other three men drag a mother and her daughter into a field to rape them. Kanbei arrives on the scene and, after the women’s servant is killed, he coldly slays the two violated women to "preserve their honor" and then kills one of the three men to create a cover story blaming him alone for the atrocity. It is at this moment that Ogami Itto passes by with his infant son, Daigoro, in his baby cart. Recognizing Itto’s reputation, Kanbei challenges him to a duel, which the Lone Wolf accepts. However, before a single blow is struck, Ogami declares the fight a draw, telling Kanbei he is a true warrior whom he hopes shall live on. This act of unexpected respect from a legendary figure deeply affects Kanbei.

Kanbei’s primary relationship is with Ogami Itto, whom he sees as a mirror—another disgraced ronin walking the demon way to hell. His entire purpose becomes fixated on proving himself in a battle to the death with Itto, perhaps seeking either validation or a honorable end. He spends the film in pursuit of this goal, finally getting his chance when he joins the army of a corrupt governor that Itto has been hired to assassinate.

Throughout the film, Kanbei experiences no clear redemption but a grim reaffirmation of his tragedy. In their final duel on a chaotic battlefield, Ogami fatally wounds him. As Kanbei dies with Ogami’s sword in his stomach, he finally explains his past, asking if his actions were truly a violation of the samurai code. Ogami’s silent acknowledgment serves as an answer, and Kanbei dies with a measure of peace, his status as a true warrior confirmed by the only man whose judgment matters to him.

In terms of ability, Kanbei is portrayed as a remarkably skilled swordsman, capable of single-handedly slaughtering a group of attackers in a fluid, balletic display of violence. His skill is such that even Ogami Itto, the former Shogunate Executioner, acknowledges him as an equal and a true warrior, which is a rare distinction. His primary role is not as a villain but as a philosophical challenger to Itto, representing the tragic consequences of a rigid honor system that punishes effective action and loyalty, providing a deep exploration of what it truly means to be a samurai.