Rui Saionji

Rui is a teenage girl with brown hair worn in a ponytail and eyes of a blue-gray shade. Through the whole episode she keeps to tennis gear: a green polo shirt, a white skirt, white sneakers, and a green band around her head.

She attends Juban Public Middle School and has already made a name as a tennis star. Her bond with Naru reaches back to childhood, born of their mothers' friendship, which leads Naru to look up to her as a kind of big sister.

Rui holds the grim distinction of being Nephrite's first energy target. On the court she faces Usagi in a match watched by Naru and a crowd of students, when Nephrite, posing as the civilian Masato Sanjoin, vaults the fence. He borrows a racket, drives home a ferocious serve that hurts Rui's wrist and knocks her own racket loose, and plants a youma and his crest into the equipment. The moment it is handed back, the youma's pull takes hold: Rui plays harder and grows stronger with every rally, her manner darkening into something cruel and violent that unsettles Naru. When Naru and Usagi track her down at the tennis school, she is tormenting two young male players, and as her energy crests it releases the youma Tesuni, which siphons her power and drops her unconscious. Once Sailor Moon and Tuxedo Mask put Tesuni down, Rui comes back to herself with no memory of the ordeal, to Naru's great relief.