Saten Ruiko

is a supporting character in the Toaru Kagaku no Railgun side stories. She is voiced by Kanae Ito.

A Level 0, classmate, and Uiharu's friend who is known for wearing a white flower on the left side of her hair. She is a little shameless as she sometimes flips Uiharu's skirt in public. When rumors of a special tool that increases psychic powers called the "Level Upper" spread, she considers obtaining it out of envy as she does not have any apparent powers. When she uses it, Ruiko consequently falls into a coma and gradually recovers thanks to the help of the creator of the 'Level Upper'. She first appears Toaru Kagaku no Railgun and makes a cameo appearance in the Toaru Majutsu no Index light novel series.

Under the effects of Level Upper, she displayed the ability to manipulate wind.