Gyutaro is tall, sickly pale, and covered in dark blotches, with a strangely built body: muscular limbs but an extremely thin, skeletal waist and a hunched posture. His spine sticks out, and his slanted, tired-looking eyes have green-and-orange irises with yellow sclera. The kanji for Upper Rank is carved into his right eye and Six into his left. He has messy black hair fading into lime green, uneven bangs, and a tied topknot. His face and body are marked with ink-like patterns, and he has black nails and sharp, interlocking teeth. Overall, he’s described as very ugly. Gyutaro wears baggy gray-blue pants and several dark red-and-black cloth pieces around his neck, arms, and wrists. Unlike most demons, his accessories aren’t made from his flesh. As a human, he looked similarly thin and blotchy, with pale blue eyes, bad teeth, and poor hygiene. He wore ragged clothes until working at a brothel, where he switched to a striped kimono and remained barefoot — just like in his demon form. Gyutaro is a cruel, jealous, and bitter demon shaped by a childhood of poverty and abuse. He envies anyone who seems happier or more fortunate, often mocking their strengths before killing them. His resentment runs so deep that he hurts himself when angry or jealous, and he insults others with the same cruel words once used against him. Despite being a powerful fighter with over a century of experience, Gyutaro is arrogant and sadistic, enjoying the suffering of Demon Slayers and often underestimating them. When cornered, he becomes even more vicious, inflicting brutal injuries without hesitation. Though he appears sloppy and unrefined, he’s surprisingly smart and tactical, able to analyze opponents and adapt quickly. He occasionally acknowledges others' skills, even while threatening them. Like most demons, he looks down on humans, mocking their weakness and trying to tempt Tanjiro into becoming a demon for a “stronger body.” However, beneath all his cruelty, Gyutaro deeply loves his younger sister Ume (Daki). He raised her alone and remains fiercely protective of her, even spoiling her and defending her in battle. His bond with her is the one part of his humanity he never fully lost.