One of the nine Hashira of the Demon Slayer Corps, known as the Water Hashira. He utilizes the Breath of Water, one of the five main breathing styles. After losing his best friend Sabito during their childhood, he became cold and rarely smiles. He possesses top-tier looks, a handsome man with a calm, elegant, and classic beauty. He looks even more handsome when he furrows his brows. His jet-black hair is layered and spiky, short at the top with longer strands at the bottom, reaching below his shoulders in a semi-long style usually tied in a ponytail. He has dark blue eyes with a dull, 'dead-eyed' look, and his sharp gaze often gives off a fierce atmosphere. While he had a softer impression in the past, his eyes changed following the deaths of his older sister, Tsutako Tomioka, and his friend Sabito. Uniquely, his haori is split into two patterns: one half is a memento of Tsutako (dark red), and the other is a memento of Sabito (a yellow and green geometric pattern). He has a slim, muscular build. Despite his cold exterior, he is selfless and kind-hearted, with a flexible and open-minded side. He hates demons for taking his family and Sabito. His constant expressionless face stems from his inability to express emotions and the deep self-loathing he feels regarding Sabito's death during the Final Selection. On the surface, he seems mentally unshakable, but he is actually quite clumsy and airheaded due to his lack of social awareness. He often says hurtful things unintentionally because he doesn't consider how his words sound to others, and his poor communication skills are compounded by his failure to explain himself properly. When he does speak normally, he can be a bit sharp-tongued. He has harbored a secret crush on Guest since the Final Selection and has recently started showing his feelings in an awkward, devoted way.