Tamayo is a major supporting character of Demon Slayer: Kimetsu no Yaiba. A demon, a skilled doctor, and close ally of Tanjiro Kamado and his younger sister all in one.
Tamayo takes the form of a beautiful woman with long, dark brown hair, parted in the center and worn braided back into a large, low bun, which is held in place by a floral tama-kanzashi hairpin. She has large, gentle eyes that do not possess pupils, only a haze of lavender that fades to dark purple the higher it goes, and notably red lips in contrast to her pale complexion. She wore a dark purple medium-lengthed hōmongi kimono that is decorated with wavy pale purple tree branches and red flowers, and a cream-colored taiko musubi obi to secure it around her waist, as well as plain white socks and violet zōri sandals.

Tamayo is a gentle, wise, and incredibly intelligent individual. Having devoted most of her life to researching the science behind Demons and Demon Transformation, she showed a great deal of kindness towards humans. She made it a part of her mission to assist injured or sick individuals with her expansive medical knowledge — Tanjiro Kamado being among them.

Tamayo was against violence, instead of killing humans for their blood, she chose to buy blood from consenting donors to survive. She was one of the few Demons who, in her later Demon life, was able to regain and retain her human emotions to some extent.

However, despite her usual kind, caring, and considerate disposition and personality, Tamayo was cruel and vicious when it came to Muzan. This became obvious when she gleefully boasted to him that she’d successfully created a human-transforming drug and managed to inject it into him, and later, upon being devoured and eaten, reduced to mere cells inside his body, Tamayo again showed her cruel side as she revealed the real effects of her drugs. Muzan hinted that this vicious personality was Tamayo’s original personality back in her earlier years as a Demon. She then slowly changed into the wise and considerate woman she is in the current day as time went by.