Gyutaro, the true holder of the Upper Rank Six position among the Twelve Kizuki, was a demon originally born human in the poorest sector of Yoshiwara's Entertainment District, the Rashomon Riverbank, where children were often seen as burdens. His human life was defined by severe hardship and neglect from the moment of his birth. His mother, afflicted with syphilis, repeatedly attempted to kill him before and after his birth due to his unpleasant appearance, a result of congenital syphilis. He survived by scavenging insects, rodents, and scraps, enduring relentless ridicule and abuse for his disfigurement and poor hygiene. The sole bright point in Gyutaro's existence was his younger sister, Ume, later known as Daki. Her beauty gave him a sense of pride and purpose. He worked as a debt collector for a brothel, a role that earned him fear and deepened his isolation. When Ume was thirteen, she was brutally burned alive and left to die as punishment for attacking a samurai who had insulted Gyutaro. Returning to find her near death, Gyutaro was assaulted by the same samurai but succeeded in killing both him and the brothel manager responsible. Carrying Ume's body, he pleaded for help but was rejected by all, eventually collapsing exhausted in the snow. The siblings were then found by the demon Doma, Upper Rank Two, who offered them his blood, transforming them into demons to preserve their lives. As a demon, Gyutaro shared the Upper Rank Six position with his sister, inhabiting the Entertainment District and primarily hunting its residents. Over more than a century, he killed and consumed fifteen Hashira, while Daki killed seven. Gyutaro usually remained concealed within Daki's body, emerging only when she faced grave peril. His demonic form retained human-like traits but was distinctly monstrous. He possessed a gray complexion marked with black blotches, sharp green eyes featuring yellow sclera and the kanji for Upper Rank and Six etched into them, and unruly black-and-green hair. His physique was oddly proportioned, with a muscular upper body and arms but an extremely thin, skeletal waist. He wore only baggy blue pants and red cloth pieces around his neck and arms. Gyutaro's personality was deeply scarred by his traumatic human experiences. He was cruel, vengeful, and envious of those with beauty, wealth, or happiness, believing that causing suffering was justified retribution for his own misfortunes. He often sarcastically praised people's advantages before trying to kill them and had a habit of scratching himself until he bled when angered or frustrated. Despite his brutality, Gyutaro demonstrated sharp tactical intelligence, analyzing opponents and adapting his strategies in combat. His most defining characteristic was his profound and genuine love for his sister. He was fiercely protective of Daki, permitting her to act freely and often indulging her, though this deep bond sometimes resulted in heated arguments and mutual blame under stress. Gyutaro's abilities were formidable. He wielded two flesh kama, sickle-like weapons formed from his own body, which he could throw and control telekinetically. His Blood Demon Art, known as Blood Scythes or Splatter Sickle, enabled him to generate sharp, projectile-like blades from his blood. These blood blades could be maneuvered after launch, form defensive domes, or execute large-scale slicing attacks such as the Circular Slicing Flying Blood Sickles. His blood was highly poisonous, capable of weakening even Hashira. A unique biological aspect was his fusion with Daki; they could only be truly killed if both were decapitated simultaneously. He could share his vision with her and communicate seamlessly during battle, making them a highly coordinated pair. During the battle in the Entertainment District, Gyutaro emerged after Tanjiro Kamado beheaded Daki, immediately reattaching her head and engaging the Sound Hashira, Tengen Uzui, and other Demon Slayers. The fight was intense, with Gyutaro employing his poison, blood techniques, and tactical mind to overwhelm his opponents, severely injuring Tengen and nearly killing others. The struggle culminated in a final clash where Zenitsu Agatsuma and Inosuke Hashibira decapitated Daki while Tanjiro and Tengen simultaneously decapitated Gyutaro. Even after decapitation, Gyutaro's body unleashed a final poisonous blood explosion that nearly killed the remaining combatants. As they disintegrated, Gyutaro and Daki initially exchanged bitter accusations and blame. Yet in their final moments, Gyutaro's true feelings surfaced. He expressed that his only regret was the negative influence he had on his sister's life, believing she could have had a better existence without him. He wished for her to be reborn into a happier life far from his influence. Daki, still clinging to him, refused separation, and they departed into the afterlife together.