Hitomi Naruse works as a nurse in a hospital's special ward, sharing duties with her younger sister Chika under Dr. Ryouko Makimura. She maintains a reserved and calm demeanor, distinct from her sister. Her responsibilities encompass standard nursing tasks within this specialized unit.

While on a night shift, Hitomi hears suspicious sounds and investigates, inadvertently witnessing a sexual encounter between Dr. Makimura and another nurse, Kaname. This event reveals Dr. Makimura's intersex condition to Hitomi, causing profound shock. Although visibly uncomfortable around both individuals afterward, the experience simultaneously sparks a deep fascination within her.

Hitomi later participates in Dr. Makimura's experimental activities. These involve intimate clinical trials testing experimental drugs for infertility treatment. Her involvement in these procedures results in the loss of her virginity. This participation signifies a significant shift in her personal and professional path within the special ward's operations.