Rei

Rei is a minor character in Demon Slayer: Kimetsu no Yaiba. She was a human wife of Muzan Kibutsuji.

Appearance
Rei was a young woman of average height. She had large brown eyes, fair skin, and black hair styled in a neat bun. She appears to be of similar age to Muzan. She was seen wearing a white cloche hat, ornate blue colored earrings, and a white and powder blue dress.

Personality
Rei was a kind and loving person, as evident by her affection towards both her daughter and to her husband "Tsuhikiko". She was confused at Tanjiro's behavior and attire and became frightened by the sudden appearance and attack of a demon, showing that as a normal civilian, she had no knowledge of the ancient war happening between demons and Demon Slayers. She lived blissfully unaware from the fact that she was the fake wife of a horrendously monstrous being.

Asakusa Arc
In Asakusa, Rei meets with her husband and daughter in a crowded street when she sees him being accosted by a boy in unusual clothes and wielding a sword. She asks Muzan on who the boy is and if he recognizes him, to which Muzan answers that he does not, stating the boy has mistaken him for someone else. Suddenly, a commotion occurs close to them; a man has suddenly transformed into a demon and attacked his wife. Rei grows scared at the situation, unknowing that Muzan is the cause of the transformation and the boy is a Demon Slayer named Tanjiro Kamado attempting to kill him.

Tanjiro is forced to restrain the demon, while Rei watches in shock. Muzan suggests they move elsewhere and they leave the scene. She then hears as Tanjiro addresses him as "Muzan Kibutsuji" and declares that he will find him, worrying her over his behavior. Later, in another part of Asakusa, Rei and her daughter are taken to a taxi service: Muzan claims he has a business meeting to attend to and will also ask the police on the strange disturbance, soothing Rei's concern. Muzan instructs the taxi driver to take them back home.

Entertainment District Arc
Though Rei is no longer seen after leaving Muzan in a taxi with her daughter, his new and established disguise as the son of a childless couple, coupled with his strong contempt for humanity, make it extremely unlikely that she and her child survived Muzan's wrath.

Abilities
As an ordinary human, Rei does not posses any additional power or abilities.