Himeno Ryuguuji hails from a wealthy family and holds the position of Student Council President. She displays pronounced arrogance and a sense of superiority, particularly targeting Satou Futoshi, whom she deems inferior and subjects to intense bullying. This includes verbal abuse and physical contempt, such as demanding her uniform be incinerated if Futoshi touches it, viewing him as contaminating. Her background includes an engagement to a fiancé, aligning with her family's social status. She engages in figure skating and demonstrates a propensity for infidelity.

A pivotal change occurs when Futoshi gains control over her using a hypnosis-capable phone, manipulating her mind to impose forced sexual fantasies and blackmail. He utilizes compromising photographs to enforce compliance, coercing non-consensual acts like simulating a first kiss with his genitalia. Continuous hypnosis and psychological manipulation lead to her total subjugation, transforming her demeanor from arrogance to subservience. She addresses Futoshi as "master" and obeys his commands without question.

Her development involves becoming pregnant by Futoshi, though the pregnancy ends in miscarriage. In her final depicted scene, she engages in sexual intercourse with Futoshi while her fiancé observes, underscoring her complete psychological domination and loss of autonomy.

Physically, she possesses waist-length blonde curly hair and blue eyes. Her typical attire consists of a school uniform with thigh-high stockings and a school crest.