Ekurok's Brother is a minor antagonist featured in the Golden Kamuy manga and its anime adaptation. He is an escaped convict from Kabato Prison who, along with his brother Ekurok and other fugitives, impersonates the Ainu people to hide from authorities and ambush travelers. Before his incarceration, he was a member of the yakuza, a past evidenced by the traditional tattoos adorning both of his lower legs. His escape from Kabato Prison was facilitated by a man named Kiyohiro Suzukawa, after which he and his cohort took over an Ainu village, forcing the women to become their wives and systematically murdering any visitors.

In terms of appearance, Ekurok's Brother has medium-length dark hair that reaches his shoulders, prominent dark eyebrows, and a dark goatee. He wears traditional Ainu clothing as part of his disguise and is typically barefoot. His personality is characterized by deception and a lack of moral restraint. He possesses some basic knowledge of the Ainu language, which he uses to maintain his false identity, but he has no qualms about harming others, including the young Ainu girl Asirpa.

His primary motivation is survival and the continued ability to evade the authorities while maintaining control over the stolen village. He follows the orders of the group's leader, Retanno Ekasi, and works alongside his brother to maintain their cover. His role in the story is brief but pivotal. When Sugimoto's group arrives at the village seeking rest, Ekurok's Brother is tasked with escorting Asirpa to the bathroom. Instead, he leads her to another hut where fellow convict Chouan Kumagishi is waiting, having her bound and gagged to prevent her from exposing their ruse. When Sugimoto becomes suspicious of Asirpa's absence and strikes him with a kisarri, a traditional Ainu knife, Ekurok's Brother becomes enraged and threatens to call out to his allies to have the girl killed. Before he can act, Sugimoto shoves the knife into his mouth and twists his neck, killing him instantly.

His key relationship is with his brother, Ekurok, with whom he conspires. They speak quietly to each other during the tense standoff with Sugimoto's party, coordinating their lies. There is no significant development for the character, as he is introduced and killed within a short sequence of events. His notable abilities are limited to his deceptive skills and his physical strength as a former yakuza and convict, though he is subdued before he can demonstrate any significant combat prowess. Following his death, he is buried alongside his brother and the other deceased convicts.