Gyuutarou has black spot birth marks tracing over his face and body. He has black hair with bangs and a mop hairstyle. He view himself as ugly when he was a human even as a demon. He has muscular arm and leg, but his chest to waist is bony and very skinny.
Gyuutarou's human memories are hazy and incomplete, save for his name.
After a tantrum-throwing Daki called out for him, Gyuutarou emerged from her body, quickly taking her to another part of the room. He reattached her severed head, comforting her while doing so. Uzui Tengen attacked the pair, but Gyuutarou quickly countered it, injuring the Pillar. He then complimented the Demon Hunter on stopping his attack.
The mysterious Demon further complimented Tengen's face, skin, flesh, and height, as well as his presumed popularity with women. Feeling envious of the Pillar, Gyuutarou threatened him with a painful death. Hearing Daki's complaints about Kamado Nezuko's involvement, he promised to exact vengeance upon all those who had hurt her. Throwing his sickle-like weapons with great force, which returned to him shortly afterwards, Gyuutarou was unable to injure Tengen or the bystanders he was protecting. He restated his envy of the Pillar, which only increased when the Demon Hunter revealed he had three wives. The mysterious Demon unleashed his Blood Demon technique, Splatter Sickle, a barrage of blood blades. His attack accomplished nothing, as Tengen escaped through a hole he made in the floor, which surprised the emaciated Demon. Gyuutarou commanded his attack to turn, revealing its auto-tracking nature. Tengen deflected the attack again, throwing and then detonating several small bombs in Gyuutarou's vicinity. Wrapped in his sister's sash, Gyuutarou withstood the blast, smugly stating they are one.
The emaciated Demon informed his opponent he was different from the previous Pillars he had fought, once again expressing his envy at Tengen's talents. He remained silent as the Sound Pillar rejected his claims, who cited Himejima Gyoumei and Tokitou Muichirou as examples of amazing talent, but countered by demanding to know how his Blood Sickle's poison hadn't killed the Demon Hunter yet. Moments later, Gyuutarou grinned, declaring Tengen's statement of poison resistance to be a bluff, and blocked the Pillar's twins blades with his dual sickles. Clashing briefly with his opponent, Gyuutarou was furious at Tengen kicking his sister. He was then surprised as Tengen threw more bombs at him and his sister, which he managed to escape unscathed. He quickly deduced the true nature of the bombs, special gunpowder capable of hurting Demons, leaving him confident in their eventual victory, but was surprised as Tengen's subsequent sword strike extended. Marveling at the Pillar's grip strength, Gyuutarou deflected the attack, but was left with a slight wound to his neck. He warned Tengen of his impending death, only to be surprised by the arrival of Hashibira Inosuke and Agatsuma Zenitsu.
The mysterious Demon reiterated his death threat, believing the arrival of the Pillar's subordinates to be insufficient. Tengen remained confident in their victory, having deduced that cutting off both of the siblings' heads off at the same time was the key to success, but Gyuutarou assured him it wouldn't be easy to accomplish. He also mentioned how he and his sister had eaten numerous Pillars, fifteen and seven, respectively. He then watched silently as Daki was taken onto the roof by Zenitsu, with Inosuke going to assist the towheaded youth in his fight, but remained confident that she would prevail. Utilizing his connection with his sibling, Gyuutarou closed one of his eyes, and quickly attacked Kamado Tanjirou. He nearly struck a blow to the youth's neck, but was thwarted by Tengen at the last second, and proceeded to exchange a flurry of blows with his opponent. In the middle of this clash, sashes from his sister's conflict above them descended, prompting Gyuutarou to call Tengen's claim of success to be a lie, as well as labeling his adversaries as incompetent for lack of movement control.