Yuki Saegusa is a teenage girl with blue hair styled in a waist-length ponytail secured by a ribbon and green eyes, matching her youthful adolescent appearance. She lives unsupervised in the large Saegusa family manor due to her father's prolonged absence. Alongside her sister, Shizuka Saegusa, Yuki actively recruits individuals to serve as submissive "pets" for their amusement and training. Her methods include entrapping unsuspecting visitors; for instance, she and Shizuka drugged Hiroko's tea when she arrived as Yuki's tutor, leading to Hiroko's unconsciousness, restraint, and induction as their captive. This exploitative pattern extends to other household members, like their stepmother Yoshie, who previously fell victim, indicating a recurring family dynamic. The Saegusa household conceals additional secrets beyond these activities. Yuki's role and personality remain consistent throughout the existing media, with her actions persistently focused on the family's exploitative practices.