He is a demon affiliated with the Twelve Kizuki, holding the position of Upper Rank Six, a position he shared with his younger sister Daki. Over a century ago during the Edo period, Gyutaro was a human who worked as a debt collector in the Rashomon Riverbank of Yoshiwara, the lowest class in the Entertainment District, before he and Daki were turned into demons personally by Doma, who was Upper Rank Six at the time. Gyutaro was cruel, ruthless, petty, and envious of anyone blessed with a better life than him, owing to a life of near-constant poverty and the harsh tragedies he experienced whilst human. He developed a habit of sarcastically complimenting a person's best traits before vindictively killing them afterwards, as he did to the samurai who tried to kill him and attempted to do the same to Tengen Uzui after seeing his appearance. Because of the hardships he faced as a human, Gyutaro attained a personal belief that to take from those who have a better life than he had as a human was justified. A habit that developed from this belief was the penchant to inflict harm to himself whenever he was angry, frustrated or jealous, as seen when he scratched himself hard enough to tear deep wounds into his own flesh when he grew jealous of Tengen. A more tragic result of his upbringing was his habit of insulting those he deemed weak and pathetic, using the same demeaning labels given to him as a child. Having lived over a hundred years and battled many Demon Slayers and Hashira, Gyutaro became arrogant and prideful in combat, developing the habit of underestimating his opponents and looking down on them as beneath him, as he did with the team of Demon Slayers dispatched to kill him by having his sister fight and deal with them first rather than himself. He has also showed himself to be intensely sadistic, revelling in the brutalization of the Demon Slayers. However, Gyutaro could also be extremely barbarous and wrathful. Outwardly, Gyutaro was unrefined and inelegant, speaking informally with a slurred and raspy voice. Despite his torpid appearance, however, Gyutaro was very tactical and intelligent, expertly analyzing his unorthodox shinobi opponent and planning his fighting style accordingly. Like his sister Daki, and demons in general, Gyutaro had a scornful view of humans and their supposed inferiority. Despite his negative traits, Gyutaro possessed a genuine, strong love for his younger sister. As the true Upper Rank Six, Gyutaro was an extremely powerful demon with over a century's worth of combat experience under his belt, having killed and devoured 15 Hashira in the past.