Benma Hidari is one of three primary antagonists in the film Lone Wolf and Cub: Baby Cart at the River Styx. He is a member of a trio of elite swordsmen known as the Masters of Death or the Gods of Death, alongside his associates Kuruma Hidari and Tenma Hidari. In the story, these three are formidable warriors hired by the Shogunate to act as escorts, protecting a traitorous artisan who holds the secret to the Awa clan's valuable indigo dye as he is transported to Edo. Benma Hidari’s role is that of a highly skilled obstacle standing in the way of the protagonist, the assassin Ogami Itto.

In terms of personality, Benma Hidari is characterized by a deep, almost artistic obsession with the craft of killing. He does not view combat solely as a means to an end but as an aesthetic pursuit. This is most powerfully demonstrated in his final moments. After being bested by Ogami Itto, who slashes his neck diagonally, Benma does not express fear or rage. Instead, he listens intently to the sound of his own blood spouting from the wound. He identifies this specific noise as mogari-bue, the whistle of a fallen tiger, a legendary and beautiful sound produced by a perfect diagonal cut. He reveals that he has always wished to kill someone just once to create such a fine cut and hear this tune, finding a dark and profound irony in the fact that he is finally hearing it from his own neck. This final speech reveals a warrior who is philosophical, fatalistic, and possesses a detached appreciation for the beauty within death, even his own.

Benma Hidari’s primary motivation is the pursuit of perfection in his deadly art. The chance to face a swordsman of Ogami Itto’s caliber represents the ultimate test, and even in defeat, he achieves a kind of fulfillment by witnessing the sublime quality of the cut that kills him. His relationship with the other two Masters of Death, Kuruma and Tenma, is that of a peer and ally, as they function as a coordinated and deadly unit. The three brothers represent a collective challenge for Ogami Itto, though Benma’s individual confrontation becomes the most memorable.

His development is contained within his single, fatal duel. He undergoes no transformation over the course of the film, but his character is fully realized and revealed in the moment of his death. His final speech serves as a complete articulation of his lifelong philosophy, turning his demise into the defining statement of his character. Regarding notable abilities, Benma Hidari is clearly a master swordsman of the highest order, as he is selected for the elite Shogunate escort mission. The specific quality of his skill is reflected in the fact that he can recognize and appreciate the technical brilliance of the cut that kills him, a mogari-bue, indicating that his expertise allows him to perceive artistry even when he is its victim.