Tokisaka Yukari, younger sister of detective Reiji Tokisaka, balances her studies at Ouba Girls Academy and membership in the art club with managing the Tokisaka household following their parents' death. She handles domestic chores and periodically cleans Reiji's office due to his helplessness in such matters, establishing herself as a reliable, composed, yet somewhat socially detached pillar of the family.

Yukari maintains a strong interest in entomology, keeping various insects in her room. This hobby sometimes results in unexpected insect appearances during meals, unsettling others. Academically inclined like her brother, her specific focus rests on insects.

She periodically aids Reiji in investigations, particularly those involving students or activities connected to Ouba Girls Academy, leveraging her access to the school and her observational skills.

Approximately two years after the initial "Girl in the Shell" case, Yukari intervenes to prevent Tomoyuki Masaki's suicide attempt at Inokashira Park. This leads to Masaki's temporary employment at the Tokisaka Detective Agency after hospitalization. During this period, Yukari continues her studies at Ouba Girls Academy, having advanced one year. The school environment, affected by prior losses, sees Yukari form new friendships, like with the quiet, awkward transfer student Yukiko Kayahara, gradually helping Yukiko integrate socially.

Her personality remains consistent: calm, responsible in domestic duties, and devoted to supporting her brother. Her entomology interest persists as a defining trait alongside her ongoing participation in the art club and her role as a stabilizing force within the Tokisaka household amid surrounding tragedies.