Ren Nanase, a 22-year-old nurse at St. Juliana Hospital, greets others with a bright and friendly demeanor, initially forming a warm rapport with new doctor Ryuji Hirasaka as both friend and superior. Her appearance features incredibly long maroon hair typically tied in a ponytail, blue eyes, and standard nurse attire.

Her life intertwines with inpatient boxer Naoya Ohkawa through a romantic relationship that spirals into match-fixing. Ryuji uncovers this secret and weaponizes it as blackmail, coercing her into degrading acts and sexual exploitation within a hospital program designed for patients' sexual interests.

Despite enduring abhorrent treatment, Ren develops an emotional attachment to Ryuji, exhibiting Stockholm syndrome symptoms. This psychological dependency intensifies into a complex, distorted bond. During this period, she becomes pregnant.

Her narrative diverges across official conclusions. In one outcome, she kills Ryuji after he revives from another character's suicide attempt. Arrested, she openly confesses her love for him. An alternate storyline in "Night Shift Nurses Kranke" depicts her marrying Ryuji; they relocate to the countryside where she serves as his wife and collaborates in his experiments.

A dedicated OVA expands her story, centering on escalating depravity orchestrated by a separate figure called "Sensei." This arc portrays extreme degradation—including coerced defecation and sexual acts near her hospitalized mother—framed through fragmented memories and diary entries that expose her psychological unraveling and the normalization of abuse in the hospital.

Ren extends beyond the main series into related media, consistently defined by her victimization, psychological complexity, and eventual transformation into a compliant participant within the exploitative system.