Ren Nanase is a 22-year-old nurse employed at St. Juliana Hospital, recognized for her bright and friendly demeanor. She has long maroon hair, typically tied into a ponytail that reaches her hips, and blue eyes.

Her background includes a romantic relationship with an inpatient boxer, Naoya Ohkawa. This relationship draws her into match-fixing, a secret that is later discovered and used to blackmail her.

She becomes a victim of systematic abuse and inhumane experiments, which result in her developing an emotional attachment to her primary abuser, a condition identified as Stockholm syndrome. Despite the abuse, she grows emotionally attached and compliant.

A significant development in her story is a pregnancy. After her abuser regains consciousness, she kills him and is subsequently arrested. During her arrest, she admits to loving him.

In an alternate storyline, she marries her abuser, Ryuji Hirasaka, and the couple relocates to the countryside. There, she assumes the role of his wife and they continue their experiments together.

Within the context of a visual novel, a different backstory is presented where she is a nursing student at St. Cadenza Nursing School. In this narrative, she is identified as a target for a lecturer named Tosatsu Koichi, who plans to conduct unethical experiments on her after being inspired by a report written by Ryuji Hirasaka.