Yukiko Minase lives as Taki Minase's cousin and legal guardian, sharing a home and a relationship dynamic akin to siblings. She manages caretaking duties like meal preparation, though her graduate studies and part-time work frequently pull her away, requiring neighbor Kurumi Imari's help with household tasks. Academically, Yukiko began in French literature before shifting to medical or biological studies. Her fluency in French, English, and Latin allows her to translate parts of the occult grimoire "Bible Black" for Taki, though she dismisses its content as perverse fantasy. Physically, Yukiko possesses gold eyes and gray-greenish hair styled similarly to Taki's. She is notably busty. At home, she favors revealing attire: a distinctive half-black, half-white suspender bra paired with light-blue mini shorts or skimpy panties. Academic settings see her in a purple shirt (without a bra), lab coat, stockings with a garter belt, or a lilac polo shirt with orange overalls for housework. A silver fish-shaped pendant necklace is a consistent accessory. Her personality blends a strong-willed, teasing nature with methodical habits. She openly flaunts her body to provoke Taki, rarely knocks before entering his room, and retaliates fiercely when wronged. Despite flirtatious behavior and expressed desire for a boyfriend, she remains a virgin with no confirmed romantic relationships prior to the depicted events. Her character arc centers on supernatural corruption. After Taki, influenced by dark magic, gropes her breast and nipple, Yukiko experiences relentless, intense arousal. This compels frantic masturbation first in her bedroom, then in a school bathroom during class hours. The effects persist into the next day, depicted in *Bible Black: Only*, driving her back to a campus restroom. Subsequently summoned by a professor, she eventually acquiesces to sadomasochistic acts in his office, including leashing and bodily penetration. Later, finding Rika Shiraki in Taki's room, Yukiko is ambushed by robed followers of Reika Kitami. Both women suffer repeated gang rape until Taki intervenes. Afterward, Yukiko displays resilience, showing no lasting trauma, and is last seen playfully ushering Taki out. Across broader game narratives, her experiences vary. In *Bible Black: La Noche de Walpurgis*, she may be corrupted by Taki's magic leading to aggressive masturbation, or raped by antagonists under Saeki's command. In *Bible Black: The Infection*, she participates in a trance-like orgy in the school basement before being rescued by Taki using a talisman.