Tamayo

Tamayo is a doctor and close ally of Kamado Tanjirou. She was turned into a Demon by Kibutsuji Muzan.

Asakusa Arc
As a trio of policemen attempted to pull Kamado Tanjirou off of a recently created Demon, Tamayo used Blood Bewitchment: Aroma of Visual Fantasy to confuse their senses. She and Yushiro approached the surprised Demon Hunter, with the Demon doctor pledging her support to him due to his insistence of referring to Demons as people. She acknowledged her own status as a Demon, stating that she wished to eliminate Kibutsuji Muzan.

Later, at her hideout, Tamayo welcomed Yushiro and Tanjirou back to the space, explaining the status of the earlier Demon and his wife to Tanjirou and reprimanding Yushiro for resorting to violence at Tanjirou's question. She then introduced herself and her colleague, answering Tanjirou's earlier question by explaining her unique ability to manipulate her body at whim, as well as her and Yushiro's shared needing of only a little human blood to survive. She further explained that she is the one who transformed Yushiro into a Demon, and reprimands the latter once more for getting violent with Tanjirou.

Tamayo informed Tanjirou that she wouldn't increase the number of Demons, but would offer it as a choice to those who were dying. Tanjirou then asked her if there was a way to turn Demons back into humans, to which she answered there was one. After reprimanding Yushiro once again for his overly violent behavior, she explained that currently she could not perform this procedure, as first she needed to research and develop it, and thus would need two things from him: blood from Demons with Kibutsuji Muzan's own blood running through them, and a chance to study his sister's blood. Explaining to him the danger of her first request, Tamayo asked the young Demon Hunter if he would still accept her request, smiling and agreeing with his statement that other people would be saved alongside Nezuko if they were successful. She was then shielded by Yushiro as a handball suddenly tore through the room.