Rei Kakizaki is a participant in the Platonic Heart tournament who works as a flight attendant to financially support her younger brother afflicted by an incurable disease. After her parents died during her youth, she assumed responsibility for her brother’s care and medical costs, a situation that compelled her to enter the tournament.

She stands 172 cm tall with a striking figure, black hair, and black eyes. Her measurements are 89-60-89. Rei is typically attired in her airline uniform, consisting of a suit, dress shirt, red scarf, heels, stockings, and a short skirt, accessorized with earrings and a wristwatch.

Her personality is serious and caring, marked by a powerful sense of duty toward her brother. She takes pride in her profession, often weaving flight attendant-themed phrases into her combat dialogue. Though life has hardened her, she occasionally dispenses wisdom about self-reliance. She also possesses a volatile temper that can provoke recklessness in battle when she is insulted or challenged.

Rei employs a tactical fighting style utilizing modified gadgets: a handbag equipped with retractable blades, a scarf concealing hidden needles, night vision goggles, and a flying suitcase apparatus. She favors long-range attacks and psychological warfare but remains proficient in physical combat.

She first appears dominating Miko Kazuki in a match but is ultimately defeated by Aya Iseshima. Seeking retribution, Rei later stalks Aya and confronts her in a darkened park, taking Haruki Honma hostage to compel Aya’s surrender. Despite deploying varied strategies and gadgets, she is defeated a second time.

After this loss, tournament organizers capture Rei and subject her to mental conditioning that shatters her sanity. She is subsequently used as a warning to other contestants about the consequences of failure. Her brother passes away during these events, though due to her altered mental state, she remains unaware of his death.