Ruiko Saten

A Level 0 classmate and friend of Uiharu who is known for wearing a flower on the left side of her hair. She is a little shameless as she sometimes flips Uiharus 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. Source: Wikipedia