Ryou Shirogane (白金 稜, Shirogane Ryō) is a wealthy high school student, the head of the Mew Project, and the owner of the Cafe Mew Mew. He also created the robot assistants of Mew Ichigo, and later Mew Berry, R2000 (Masha) and R2003 (Ucha). The Mew Project was first started by his father in the United States five years before the time when Tokyo Mew Mew is set. Ryou is said to be a genius in the manga, and in the anime series it is said that his IQ is higher than 180. At the age of ten, he had already decided he would be a scientist like his father, and had succeeded in culturing cells his father had not been able to. His father worried about involving him in the project but felt he would be able to succeed in introducing the animal genes into humans. Later the same day, a lab explosion killed both of Ryou's parents, as well as his dog Daisuke. Ryou decided to go to Japan to continue the project. When the technique for injecting the genes was ready to try, Ryou tested it on himself first to ensure the chosen girls would not be harmed. As Ryou was not a compatible host, the only effect on him was that he can change into a cat at will, but if he remains in cat form for more than ten minutes, he will remain that way permanently. Ryou tends to talk roughly but he has a very strong sense of personal responsibility, particularly for having to turn the girls into Mew Mews. He also encourages the girls in his own way, such as helping boost Lettuce's self-confidence during a party on his yacht. He enjoys teasing Ichigo and making her blush. In his cat form, he helps Ichigo when she herself changes to a cat, but does so under the name Alto. Not knowing it is Ryou, Ichigo kisses the feline Alto to help her change back three times. When she learns it was Ryou all along, she's very embarrassed. Like Keiichiro, Ryou's age is never mentioned in the anime or manga, however, in the official game guide for the 2002 Playstation game Tōkyō Myū Myū – Tōjō Shin Myū Myū! – Minna Issho ni Gohōshi Suru Nyan, he is listed as being fifteen years of age. In Mew Mew Power promotional material he is listed as being sixteen.
In the anime series, his voice actor is Kouichi Toochika. In the Mew Mew Power English adaptation his name is changed to Elliot Grant and he is voiced by Sean Schemmel.