Sakonji Urokodaki is a retired member of the Demon Slayer Corps, having previously served as the Water Hashira. A master of the Water Breathing style, he trained Makomo, Sabito, Giyu Tomioka, and Tanjiro Kamado. He is an elderly man whose face, described as gentle and calm, remains perpetually hidden behind a tengu mask. In his youth, he had black hair worn in a topknot, which has since turned silver. His usual attire consists of a cloud-patterned jinbei kimono, navy pants secured by white kyahan guards, black tabi socks, and sandals with blue straps. While traveling, he also covers his head and neck with a white cloth. Stern, disciplined, and pragmatic as a teacher, he possesses a deeply compassionate and understanding nature. He cares profoundly for his students, viewing them as family, and is haunted by those he has lost. His character is defined by an unwavering commitment to protecting humanity, a strong sense of duty, and adherence to principles like honor, integrity, and selflessness. He was one of the few to wholly trust Nezuko Kamado never to harm a human. Born into a family of farmers, his life changed when a demon attacked during a rice harvest, killing his parents and mortally wounding his brother. He was saved by a demon slayer named Yoshitaka, who revealed the existence of demons and the Demon Slayer Corps. This tragedy led him to request training from Yoshitaka and eventually join the Corps. As a slayer, he single-handedly captured the Hand Demon and imprisoned it on Mount Fujikasane. He served as the Water Hashira for nearly fifty years before retiring to become a cultivator. His involvement in the narrative begins when he receives a letter from Giyu Tomioka requesting he train Tanjiro Kamado. After encountering Tanjiro and his demon sister Nezuko, he tests Tanjiro's resolve by asking what he would do if Nezuko harmed a human. Satisfied with the answer, he takes them in. He subjects Tanjiro to a rigorous year-long training regimen on Mount Sagiri, covering swordsmanship, breathing techniques, and survival skills. The final test requires cutting a giant boulder, a feat Tanjiro achieves after an additional six months of independent effort. Before Tanjiro leaves for Final Selection, Urokodaki gives him a ceremonial haircut and a fox mask to ward off bad luck. He is deeply moved when Tanjiro returns alive from the selection, having slain the Hand Demon responsible for killing his previous students. He provides Tanjiro with a box made of "Mist Cloud Fir" to carry Nezuko and reveals he used hypnotic suggestion on her while she slept, implanting the command to protect humans and view them as family. He also educates Tanjiro about demons, their abilities, and Muzan Kibutsuji. When the Demon Slayer Corps learns of Nezuko's existence, he sends a letter to its leader, Kagaya Ubuyashiki, explaining her unique situation and vowing that he, Tanjiro, and Giyu Tomioka would all commit seppuku if she ever killed a human. During the Infinity Castle arc, he is tasked with protecting Nezuko at the Butterfly Mansion after she develops a resistance to sunlight. There, he administers the cure developed by Tamayo to revert her to a human. As Nezuko falls ill from the medicine, he tends to her, reflects on all that has happened, and mentally urges both siblings not to lose. Despite his efforts to stop her, Nezuko eventually awakens and escapes his care. As a former Water Hashira, he was once among the most powerful combatants in the Demon Slayer Corps. His abilities include full mastery of Water Breathing and its ten forms. He also possesses an enhanced sense of smell, enabling him to detect emotions, sense openings in an enemy's movements, and determine how many humans a demon has consumed. Even in old age, he demonstrates considerable speed and stealth, moving with silent swiftness. He does not drink alcohol and has a very low tolerance for it. He began wearing his mask because demons used to mock his face. He was ranked 14th in the first character popularity poll.