Student, tennis player
Mother (name unknown)
Rui is a Juuban Municipal Junior High School student and a famous tennis player. She and Naru are childhood friends because their mothers are friends, and Naru refers to her as "big sister" because of this.
Rui is a teenaged girl with brown hair in a ponytail and blue-gray eyes. She wears a green polo shirt, a white skirt, white sneakers, and a green sweatband for the entirety of the episode.
When Nephrite begins his energy collecting, his first choice is Rui Saionji.
At a tennis court, Rui is playing a game of tennis with Usagi, Naru, and a few other students watching. There, Nephrite, in a civilian disguise under the name "Masato Sanjouin", jumps over the fence and onto the tennis court. He asks Rui's opponent to lend him her racquet. He performs an extremely powerful serve, hitting Rui's wrist and knocking her racquet out of her hand. He then implants evil power and his crest onto her racquet.
When he returns it to her, Rui immediately feels the effects of the evil power, and begins to play more aggressively, and continues to become more powerful the more she plays. Her personality also becomes much more darker than before, worrying Naru.
When Naru and Usagi go to find Rui at her tennis school, Rui is in the middle of terrorizing two male tennis players. When they order her to stop, Rui's energy level peaks, unleashing the youma Tesuni, and it takes her energy, knocking her unconscious.