Kuesu was a young woman in her late adolescent years, with a fair skin complexion and well-endowed figure. She has long, straight silver (originally black, as seen in flashbacks) hair that runs all the way down to her hips with several bangs framing her forehead, and has violet eyes (a brighter shade in the anime). On her forehead is a white, crescent moon-shaped mark turned a full 90 degrees clockwise. It is because of this mark she was known by ayakashi as the "Twilight Moon" (黄昏の月, Tsaogare no Tsuki). Her attire mainly consists of gothic lolita outfits, which are usually accented with a headband on her hair with ribbons on the side. For footwear, she wears a pair of calf-high boots over black, thigh-high stockings.
In Volume 0 of the manga, it is revealed her black hair turned white as a result of her casting a forbidden magic spell to stop an evil cult that released a demon during her time in England.
As a result of her upbringing as a Demon Slayer, Kuesu shows a haughty and arrogant personality most of the time, to the point of having a superiority complex. Her most recognizable trait is her ruthlessness towards ayakashi, killing them regardless if they're friendly, as she believes it is her duty as a Demon Slayer to exterminate them. This ruthlessness is also due to the fact that her family is the most prejuduced of the twelve, being looked down upon by them and the ayakashi as heretics and outcasts for using Western magic, thus struggling to bring the family to the #1 spot by killing as many ayakashi as she can.
- Expert Spellcaster: As a descendant of the Jinguji Family, Kuesu can cast various magic spells through the spellbook she usually carries. However, she can as easily cast these spells without it (unless it's for more powerful spells). Her spells usually revolve around a fire motif, being able to cast fireballs. Similar to the Amakawa Family's power, the Jinguji Family's dark magic has only been passed down to female members of the family.
- Teleportation: Kuesu has the ability of instant teleportation. This was first shown when she teleported up to rooftop of the Shintakimiya Hotel to face off against Shizuku.
- Firearms: Although she mainly uses magic, Kuesu wields a Stechkin APS pistol loaded with magic bullets as her personal sidearm. So far, it was only used once during her duel with Himari.
- Immortality: After dying in a fight with Shuten-Doji, since is eventually revived by the Book of Truth, but in the process she becomes immortal. As such she cannot age or die as a living testament and proof of the Book of Truth's existence.
Yuto is Kuesu's fiancé. Their engagement was arranged by the Amakawa och Jinguji families when they was just children, in an attention to make the latters more powerful and respected among the other Demon Slayers. Like the other girls in his group of friends Kuesu is in love with him.
Archrival for Yuto. It is said that both Kuesu and Himari (in cat form) met while she was still a little girl.
- Among all 5 women in Yuto's harem, Kuesu is the only girl who kissed Yuto the most, causing all the girls, especially Himari, to become jealous.
- In Japanese, Kuesu means "questionable", a name that perfectly fits the girl's personality.