Kuesu Jinguji is an Demon Slayer that uses Dark Magic and she is Yuto's fiance.
Kuesu Jinguji is the heiress of the Jinguji's Family, a Demon Slayer family that uses Western Dark Magic. Kuesu is Yuto's fiance, and claiming that both of their families had promised for their future marriage. She is very arrogant and haughty as result of being upbringing, and is shown to be highly aggressive and assertive. She also has an enduring rivalry with Himari over Yuto, which it was from their first encounter in Noihara when she told Himari to stay away from him, and made Yuto allergic to cats using her magic so Himari couldn't get close to him. Prior to leaving for England to study magic, she and Yuto made a promise together to fight Ayakashi, which was forgotten due to the magic in Yuto's amulet. Like the other girls, she has feelings for Yuto, but due to him befriending Ayakashi, to her which is contradictory of his duties as a Demon Slayer. She slowly begins to accept the Ayakashi siding with him as her comrades, though this does not change her views about them.
Kuesu Jinguji is one of main characters from Omamori Himari manga series by Milan Matra. No information about her creation or what inspired her creation.
She is unfriendly person with other Demon Slayer families, as Kuesu's family was looked down upon by them and the Ayakashi as heretics and outcasts for using Western magic. The only Demon Slayer family that didn't look down to them was the Amakawa Family. Because they were one of the higher-ranking families, the Jinguji Family tried to make allies with them by marriage.
One of Kuesu's notable features is the crescent-shaped mark on her forehead (similar to the one that often appears on Sailor Moon's Usagi Tsukino). Because of this and her relentless killing of Ayakashi, she is given the infamous title of "Twilight Moon". Another notable feature is her white hair, originally was black, it turned into that color as a result of her casting a forbidden magic spell to stop an evil cult that released a demon during her time in England
Kuesu can cast various magic spells through her spellbook, she also can easily cast these spells without it and claiming that her magic powers are far more powerful than of the 10 people. She also has the ability to teleport anywhere and wields a Stechkin APS machine pistol loaded with magic bullets as her personal sidearm. Similar to the Amakawa Family's power, the Jinguji Family's dark magic has only been passed down to female members of the family.