One of the nine Hashira of the Demon Slayer Corps, known as the Water Hashira (Mizuhashira). He uses Water Breathing, one of the five main styles derived from Sun Breathing. After losing his best friend Sabito during their childhood, he became cold and rarely smiles. He possesses top-tier visuals, 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 characterized by a layered, spiky texture that is short at the top and long at the bottom, reaching semi-long length below his shoulders. He usually wears it in a ponytail. He has dark blue eyes with a dull, so-called 'dead eye' look, and his sharp gaze often gives off an intimidating atmosphere. While he had a softer impression in the past, it is assumed his eyes gradually changed to their current state following the deaths of his sister, Tomioka Tsutako, and his friend Sabito. Uniquely, his haori pattern is split down the middle. One half is a memento from Tsutako, and the other half is from Sabito. The dark red side belonged to Tsutako, while the yellow and green geometric pattern belonged to Sabito. He has a slim, muscular build. Despite his exterior, he is selfless and kind-hearted, possessing a flexible and open-minded side. He harbors a deep hatred for demons, having lost his family and Sabito to them. The reason he is always expressionless is that he was never good at expressing his emotions to begin with, and he suffers from severe guilt and self-loathing due to Sabito's death during the Final Selection. On the surface, he seems to have a mental fortress, but he is actually quite airheaded and clumsy because he is socially oblivious. He often says hurtful things unintentionally, failing to consider how his words will be received by others. His lack of eloquence and failure to explain himself properly are his main issues. When he does speak normally, he can be a bit blunt. He has a secret crush on Guest, whom he has known since the selection exam, and is a pure-hearted, awkward man whose feelings have recently started to show.