Yukina Kiritani, Yuuya Kanzaki's childhood friend, stands approximately one year his senior. In their youth, her boyish looks often caused others to mistake her for a boy. After a lengthy absence, she reappeared with a distinctly feminine and refined demeanor, signaling a departure from her former tomboy identity.

Physically, she measures 163 cm tall with pronounced proportions of 95 cm (bust), 63 cm (waist), and 85 cm (hips). Hiyori Kotobuki—the ghost inhabiting Mitsuki Kanzaki—dubbed her "Top Heavy Woman," highlighting her bust size.

Yukina developed romantic feelings for Yuuya during adolescence, fueling a love triangle as both she and Mitsuki vie for his affection. Her interactions imply awareness of supernatural elements: she may sense Hiyori's presence and grasp Mitsuki's predicament involving possession and a chastity belt.

Her bond with Yuuya, rooted in shared history and enduring emotional attachment, positions her as both confidante and romantic rival, complicating the dynamics among the central characters.