Tamayo

Tamayo is a demon who works as a doctor. Muzan Kibutsuji turned her into a demon, and she stayed under his control until Yoriichi Tsugikuni nearly killed him and spared her. She altered herself so she can survive on small amounts of blood instead of human flesh. Searching for a cure for demons, she enlists Tanjiro Kamado, who brings her Nezuko's blood and blood samples from members of the Twelve Kizuki. Apart from Muzan she is the only demon who can create demons, and she does so only for dying patients who have no other option.