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Ruiko Saten (佐天 涙子)Age: 12–13
Height: 160 cm
School: Sakugawa Middle School
A Level 0, classmate and friend of Uiharu. She wears a flower on the left side of her hair. She is cheerful and friendly, and is a little shameless as she sometimes flips Uiharu's skirt in public.
She first appears in the Toaru Kagaku no Railgun manga and its anime series and makes a cameo appearance in the Toaru Majutsu no Index light novel series and the opening of the anime.