Rie Kasatani is a Japanese high school student with vibrant orange hair styled in a shoulder-length curtain cut parted down the middle and striking green eyes. An energetic athlete, she competes in her school's track club. Her typical outfit consists of a school uniform with a ribbon tie, jeans, and thigh-high stockings.

She resides with her older sister, Youko Kasatani, a 22-year-old university student who acts as her guardian while their parents work abroad. Youko treats Rie with consistent kindness. Rie maintains a deeply strained relationship with her childhood friend and neighbor, Susumu Sakurai. She openly dislikes his introverted passivity, particularly his refusal to confront bullies, and reacts with annoyance to rumors linking them romantically.

Rie displays a rude and arrogant demeanor, especially toward Susumu, criticizing his untidiness and lack of athleticism with palpable contempt. This dynamic fractures when hypnotic manipulation targets her. Under its influence, she wrestles internally: part of her feels an unnatural pull toward Susumu, while another fiercely resists it. This conflict prevents the hypnosis from fully taking hold, trapping her between involuntary attraction and genuine revulsion.