A subordinate of Tamayo, a demon who opposes Muzan Kibutsuji independently of the Demon Slayer Corps. He is also a demon created by Tamayo, not Muzan. Tamayo turned Yushiro into a demon with his prior consent to save him as he was dying of illness. She warned him beforehand that living as a demon would be extremely painful, as he would never be able to go out in the sunlight again and his body would only be able to consume human blood. Fortunately, he can survive by drinking only a small amount of blood obtained under the guise of transfusions from people in financial need, and he usually works as a doctor alongside Tamayo. He is currently 35 years old, which is still young even by human standards. He treats his savior and beloved, Tamayo, with utmost respect and obeys her every command, but he is otherwise prickly and does not hesitate to use sharp words. Consequently, he becomes immediately jealous and wary of anyone who receives Tamayo's attention or favor, or anyone who insults her. However, he possesses a basic sense of decency and shows the height of tsundere behavior toward Tanjiro and Nezuko. Likes: Tamayo Dislikes: Tanjiro, Nezuko, anyone insulting Tamayo

He has a hairstyle with bangs that reveal his forehead similar to his sister, spiky red hair, and clear, deep red eyes. While he looks handsome in the artwork, according to the author, he is closer to being plain than handsome. In the setting, he has an average appearance and is considered unsightly specifically because of the scar on the left side of his forehead. Daki, who judges people solely on looks, called Tanjiro ugly, though she did say his eyes were pretty and threatened to pluck them out to eat. Still, he isn't treated as particularly ugly in the story; he has received compliments on his appearance, and some mentions suggest he isn't ugly at all, given his slim build and large features.

An official beauty within the series. Like her brother, she has a hairstyle that reveals her forehead. She has long hair reaching past her waist and downward-slanted eyes accented by a single upper eyelash. Unlike her siblings who have red eyes, she is the only one with pink irises. Back when she was human, she tied her hair with three small ribbons. Because she bites down on a bamboo muzzle, she can only make sounds like "Mmph!" or "Mmm~!" Likes: Tanjiro, Yushiro, Tamayo Dislikes: Demons