Rei commands the Twenties, an organization specializing in illicit courier operations, and bears the alias "Twenty Faces of Beauty". Her personal history and the specific path into criminal activity are not detailed.

Physically, Rei possesses a curvaceous figure, grey eyes, and light brown hair typically arranged in a long ponytail fastened by a large black bow. Her standard ensemble includes a black suit jacket over a red shirt, a black skirt, dark grey fishnet stockings, and black high-heeled shoes. She accessorizes with red-tinted sunglasses, a black choker, black gloves, yellow lipstick, and yellow eyeshadow. For infiltrations, such as posing as a teacher at Yubiwa Academy, she wears a black sleeveless sweater and khaki wide-leg pants, keeping her gloves and heeled shoes. The manga portrays her with shorter, straighter hair tied higher, an open suit jacket revealing her midsection, tear-drop earrings, and a necklace featuring a circular ornament.

Rei exhibits significant skill in disguise and stealth, successfully infiltrating Yubiwa Academy unnoticed. She claims escaping prison is a casual pursuit, indicating expertise in evasion. Her known operations involve a contract with a military satellite organization to kidnap Mayumi Doujima after Mayumi identified the satellite, and collaboration with Rai Fudatsuki on the development and testing of "Invisibility Wear" technology.

Her narrative role centers on antagonistic operations intersecting with cases investigated by the Pretty Boy Detective Club, particularly those involving Mayumi Doujima and technological conspiracies. Substantive character evolution or background beyond these criminal activities remains unexplored.

Her name uses the kanji for "beautiful" (麗) while phonetically aligning with "zero" (零), reflecting her leadership position. The "Twenty Faces" moniker directly references Edogawa Ranpo's literary antagonist, the Fiend with Twenty Faces, a foundational inspiration for the series.