Kenkichi Aoyama is a character from Golden Kamuy whose presence is felt most strongly through memory and its impact on another key figure, the Matagi hunter Genjirou Tanigaki. Aoyama originally came from the same mountainous region of Ani in Akita prefecture as Tanigaki, and like him, was raised in the traditions of the Matagi, the bear-hunting people of northern Japan.

In terms of his appearance, Aoyama is depicted as having a square face with a long nose, triangular eyebrows, and soft eyes. He is often shown with stubble on his chin and a shaved head with a widow's peak. His clothing reflects his dual life as both a hunter and a soldier, ranging from traditional Matagi garments, including a hood tied at the neck for warmth, to the standard uniform of the Imperial Japanese Army.

Aoyama's personality is best understood through the tragic events that define his life. He was a friendly and easygoing individual who shared a close bond with Tanigaki, joking with him and sharing food during their hunting expeditions. His deep capacity for love is shown through his relationship with Fumi, Tanigaki's younger sister, whom he married. When Fumi fell ill with smallpox, Aoyama refused to abandon her, a common but cruel practice of the time to prevent the spread of infection. Unwilling to let her die alone and in pain, he resolved to perish alongside her. However, Fumi convinced him otherwise, begging him to end her suffering so he might live and find a new purpose. Aoyama granted this wish, euthanizing her with his hunting knife. The guilt and sorrow of this act defined his remaining years. He burned down their house with her body inside and fled the village, carrying an enormous sense of remorse and a desperate wish to apologize to the Tanigaki family for the loss of their only daughter.

Driven by this loss and a desire to find a new path, Aoyama left his life as a Matagi behind and enlisted in the Imperial Japanese Army, where he was assigned to the 1st Division. His role in the story is largely a retrospective one, revealed through the flashbacks of other characters. He served in the same platoon as the protagonist, Saichi Sugimoto, and taught him about the Akita dialect and his own hunting past. The most significant relationship, however, is with his brother-in-law, Tanigaki. After Fumi's death, Tanigaki found her burned corpse and Aoyama's knife, leading him to believe that Aoyama had murdered his sister and fled. This sparked a deep-seated desire for revenge in Tanigaki, who left home to find the man who had seemingly betrayed his family.

The culmination of Aoyama's character development and his ultimate fate occurs on the battlefield. During the fierce fighting for Hill 203 in the Russo-Japanese War, a desperate Russian soldier strapped with grenades charged the Japanese trench. Aoyama, demonstrating a fearless and selfless nature, threw himself at the soldier to shield his comrades from the blast. This heroic act cost him his sight, his hearing, and the use of his legs, leaving him mortally wounded with his innards exposed. As he lay dying, he was approached by Tanigaki, though he did not recognize him. Believing he was speaking to a stranger, Aoyama confessed everything about Fumi's death and begged the man to tell her family the truth. Tanigaki, still unaware of the man's identity, offered him a piece of his homemade kane mochi, a walnut-filled rice cake. As the dying soldier tasted it, he immediately recognized the unique flavor from their shared youth. In his final moment, he whispered Tanigaki's name, bringing their anguished, separated story to a close. A notable ability, stemming from his Matagi training, was his skill as a hunter, including the use of a masuke, a traditional Matagi knife, which he used both to euthanize his wife and as part of his daily life.