Yukihime serves as the alias for Evangeline Athanasia Katherine McDowell, a vampire turned during the Hundred Years' War at age ten, locking her true form as a child. Now over 700 years old, she employs illusion magic and specialized magical pills to conceal her immortality by maintaining an adult guise. Her platinum blonde hair and blue eyes persist in both forms; the child prefers gothic lolita fashion, the adult favors business attire. After Nagi Springfield liberated her from a curse, she founded UQ Holder, a secret society protecting immortals and societal outcasts headquartered at the Senkyokan estate near Shin-Tokyo. As leader, she directed missions from combating the Ba'al uprising to investigating dangerous immortals. Approximately two years before the main events, she witnessed the fatal car accident of Tōta Konoe's parents. Honoring their dying wish, she turned Tōta into a vampire, became his guardian, and raised him while suppressing his memories of the incident. Her relationship with Tōta transcended mentorship due to temporal paradoxes. Centuries earlier, during her fledgling vampire years, she met the present-day Tōta in Dana's palace. Bonding under the alias "Kitty," she developed romantic feelings. This history resurfaced when Tōta later confessed love and proposed. She outwardly rejected him but privately acknowledged happiness, noting he was "five hundred years late." She also harbored unresolved feelings for her former student, Negi Springfield, pledging to kill him if the Mage of Beginning possessed him. As a True Ancestral Vampire with Class A immortality, she regenerates and reattaches severed limbs, though retrieval remains necessary for regrowth if limbs retain vitality. Her magical mastery focuses on ice and dark spells, including barriers, ice spears ("Iaculatio Grandinis"), and area attacks like "Anthos Pagetou Khilion Eton." She uniquely created and mastered Magia Erebea, a vampiric fusion of magic and combat, without suffering its typical corruption. Her techniques include spell-reflecting "Lunar Path" and ice-enhancing "Krystalline Basilea" armament. During the Dark Future Arc, Tōta sacrificed himself to stabilize the collapsing space elevator, fusing with the World Tree. She then battled Ialda Baoth on Pluto, defeating Negi but becoming possessed by the Mage of Beginning after casting the forbidden "Manus Jaldae." In the Final Battle Arc, this possession resolved when Negi and Tōta collaborated to save her and defeat Ialda. Her history intertwines with Negi Springfield, whom she trained 80 years prior, and Nagi Springfield, whom she married in an alternate timeline after Ialda's influence was purged from him.