Yuki is a Kangitsune, a type of weasel demon, originally sealed in the past by Haruyoshi Kugano. She was considered the most non-threatening ayakashi under his command. After his reincarnation into a new world as Seika Lamprogue, Yuki was summoned to confirm his retained ability to access ayakashi. She instantly recognized Seika as her master through his soul, despite his new form.

Her appearance features very long gray hair tied in twin ponytails secured by large beads and dark gray eyes. Previously manifesting in an adult human form, her appearance inexplicably shifted to that of a young girl in the new world. She often adopts the shape of a small white fox, concealing herself in Seika's hair.

Personality-wise, Yuki was once described as composed and beautiful. However, her demeanor became less mature and more excitable upon arrival in the new world. Despite this change, she retains deep concern for Seika's well-being and proactively cautions him against recklessness in dangerous situations. She also demonstrates perceptiveness regarding interpersonal emotions, particularly romantic feelings, a sharp contrast to Seika's obliviousness. For instance, she recognizes Yifa's affection for Seika and directly informs him of it, though he dismisses her observations.

Her abilities stem from her nature as an ayakashi bound to Seika. She serves primarily through unwavering loyalty and situational awareness rather than direct combat. Her role extends beyond a familiar; she actively participates in Seika's strategies, offers timely advice, and provides emotional support. This includes reminding him of his past trauma to prevent impulsive decisions that could repeat his history of betrayal.