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.
Tamayo wore a dark purple medium-lengthed tomesode 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.
Before in her past, Tamayo wore her hair tied in a low ponytail and had stilted pupils.
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 was one of the most knowledgeable people on the subject in the series. Despite the generally chaotic relationship between humankind and Demons, 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 had a strong preference against violence, instead of killing humans for their blood, she chose to buy blood from consenting donors to survive. She was adamant in teaching her assistant, Yushiro, against violence and often reprimanded him for his habit of hitting others. 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 has displayed a more cruel and vicious persona upon confronting Muzan. This was seen 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.
Despite this, as seen during the flashbacks hundreds of years before Muzan's meeting and battle with Yoriichi Tsugikuni, Tamayo was shown to have a more docile personality, a likely result of her realizing how impossible it was to defeat Muzan with her power to avenge her family. However, this changed upon her witnessing Yoriichi's strength and how close he came to killing Muzan, as Yoriichi noted that he saw a glint of hope in her once-deadpan eyes as she realized that he'd almost killed her former master, showing that, upon seeing Yoriichi's power, Tamayo's resolve to avenge her family was reignited.
Though very little of Tamayo's abilities are seen, given that she was Muzan Kibutsuji's personal aid before the Twelve Kizuki were even formed and that he spared her after she attempted to kill him (something he sees as anathema) means she is both very old and very powerful.
Medical Skills: Tamayo had displayed impressive skills in the fields of medicine and pharmaceuticals, possessing the skill to alter her own body so she could survive on only a small amount of human blood. She was also able to convert the terminally ill Yushiro into a Demon without Muzan's blood and is later able to reverse the process when treating the man they encountered during the Asakusa Arc. To further showcase her pharmaceutical skill, Tamayo was also able to assist Shinobu Kocho in saturating her body with deadly Wisteria poison without it so much as causing her the slightest illness; a tactic the Hashira would later use effectively against Upper Rank Two, Doma.
- Anti-Blood Demon Coagulant: Tamayo created this medicine to prevent a Demon's Blood Demon Art from progressing. Yushiro used this medicine to cure Zenitsu Agatsuma after his fight with Kaigaku.
- Anti-Kibutsuji Drug: It was later revealed that upon teaming up with Yushiro and Insect Hashira, Shinobu Kocho, Tamayo had successfully created a powerful, four-stage drug that could gravely weaken Muzan Kibutsuji. Once administered into him, its effects would be strong enough to significantly harm him despite his immense physical resistances and abilities. The first stage of the drug consisted of the same human-conversion stage that was included in the drug given to Nezuko Kamado.
- Supernatural Blood: Tamayo's main ability is to draw her blood and cast various spells that enact various effects on her targets.
Blood Bewitchment (
- Scent of Illusory Blood, Visual Dream (
視 覚 夢 幻の 香Shikaku Mugen no Kō?) - A hallucination that hinders the vision of the affected by creating beautiful flower patterns around them.
- Magical Aroma of Daylight (
白 日の 魔 香Hakujitsu no Makō?) - Acts as a truth serum, causing brain function to decrease and will make the recipient confess their lies and not keep their secrets. It can be harmful to humans.
- Tamayo's name contains the kanji for "pearl" and "world".
- Tamayo was ranked 18th in the first character popularity poll, with 138 votes.
- Her Japanese voice actress, Maaya Sakamoto, is married to Obanai's Japanese voice actor, Kenichi Suzumura.
- Tamayo is at least 500 years old, as she was shown thriving during the same time as Yoriichi Tsugikuni and was transformed into a demon sometime before that.
- After her encounter with Yoriichi, she survived on eating animal and human corpses (later transitioning to human blood). She refused to obey her demonic instincts and never attacked humans, despite how much pain she felt.
- (To Tanjiro Kamado) "You still use... the term "person"... to refer to even a transformed demon. And you're trying to save him. Allow me, then, to lend you a hand."
- (To Muzan Kibutsuji) "Today... is... the day... you... will fall... into... hell..."
- (To Muzan Kibutsuji) "The drug... I used... turns you into a human... and... I'm not telling you. Why don't you try using all those useless brain cells you now have?"
- (To Muzan Kibutsuji) "Well, well. It looks like the death you've hated for so long is right before your eyes now."
- (To Muzan Kibutsuji) "I don't need to be stronger than you to kill you. I can just make you weaker. Just as you'll do whatever it takes to stay alive, I... No, we will do whatever it takes to kill you."