Kazuo Henmi is a supporting antagonist and one of the tattooed convicts who escaped from Abashiri Prison. A serial killer of significant notoriety, his criminal history is marked by a staggering number of victims, with accounts suggesting he may have murdered over one hundred people. His seemingly unremarkable and polite demeanor belies a profoundly disturbed psyche, as prison guards noted that taking a life was as natural to him as breathing.

The origin of Henmi's murderous obsession lies in a childhood trauma. As a young boy in Shimotsuke Province, he witnessed his younger brother being eaten alive by a wild boar. The memory of the desperate struggle for life slowly fading from his sibling's eyes became a fixation. Rather than recoiling from the violence, he developed a powerful and deeply twisted desire to both kill and be killed, a fate he found sexually arousing. This desire was not for a simple or quiet death, but for a specific, violent end in the midst of a life-or-death struggle, mirroring the "shining" end he felt his brother had.

Henmi’s role in the narrative begins when he is rescued from a shipwreck by Saichi Sugimoto and Asirpa. Presenting himself as a harmless fisherman, he is taken to a coastal village, where his true nature is soon discovered. Upon learning of Sugimoto's past as a soldier who has killed many men out of necessity, Henmi becomes obsessed. Hearing regret and a haunted spirit in Sugimoto's recounting of war, Henmi instead perceives a fellow killer, a worthy adversary who might grant him the death he craves. His primary motivation becomes forcing a confrontation with Sugimoto, seeing him as the ideal instrument for his own self-destruction.

Key relationships are largely defined by this singular obsession. His interactions with Sugimoto are framed by a deadly game of hunter and hunted, where Henmi attempts to kill Sugimoto while simultaneously hoping to be killed by him. He forms a brief and opportunistic alliance with the escape artist Yoshitake Shiraishi, having been his cellmate in Abashiri. However, this connection is purely transactional and is overshadowed by Henmi's fixation on Sugimoto. His relationship with the other main cast, including Asirpa, is one of immediate threat, as she quickly recognizes the danger he poses.

Henmi’s development is less an arc of change and more a relentless pursuit of his deadly aesthetic. He is shown to be cunning and patient, capable of strangling a man to death while maintaining a cordial conversation with Sugimoto only a short distance away. His psychological state remains constant, driven by the singular goal of achieving a "gleaming" death in a savage fight. This culmination occurs when he finally battles Sugimoto, an encounter where he is mortally wounded but experiences a euphoric satisfaction, believing his wish is being fulfilled.

In terms of abilities, Henmi is a deceptive and effective predator. His primary weapon is his unassuming and sociable personality, which allows him to approach victims without raising alarm. He is also skilled with a knife, capable of swift and silent lethal attacks. Beyond his physical capabilities, he possesses a cunning intellect, often leaving clues and carving the kanji for "eye" into his victims' corpses, turning murder into a kind of personal performance designed to create a challenge for his pursuers. His chilling pathology and the lengths to which he will go to achieve his specific vision of death make him a uniquely formidable and disturbing figure.