Rei is a charming girl attending the second year at Seiran. Nanako meets her for the first time in the bus taking her and Tomoko to their first day in the new high school. Nanako is immediately impressed by her beauty, her confident attitude, and most of all by her "warm and deep" voice.

Just like Kaoru, she's an androgynous beauty: she always wears dark man clothes, is a rebel (she smokes uncaring of school rules and likes throwing knives in the old clock tower); she's a very sensitive and tormented soul (she reads and recites Verlaine's poems), she's worshipped by all the youngest students (she plays basketball, plays in the school theatre, she can play wonderfully the piano, the flute, the violin—and guitar in the manga). However, everywhere Rei goes, she always takes with her a wide range of pills, that help her forget or ease the pain in her soul, caused mainly by her mysterious and complicated relationship with Lady Miya.

Rei's nickname comes from Louis-Antoine de Saint-Just, the historic character from French Revolution who sent many opponents to death by guillotine, famous for his cold beauty and called "The Angel of Death." And exactly like the person she takes her name from, Rei's eyes, with "non-human and superior attitude" "attentively observe an undefined and distant point, maybe death..." as Nanako says reading Saint Just's biography.