Shirai, Kuroko

Mikoto's junior in Tokiwadai Middle School and a protagonist in Toaru Kagaku no Railgun and main character in the eighth volume of the Toaru Majutsu no Index light novels.

A Level 4 ESPer, she is a member of Judgment, a special public committee group whose duty is to maintain peace and order in Academy City. She has an unhealthy obsession with Mikoto, who she calls "Onee-sama" (big sister); she is on the constant lookout for a chance to get physically intimate with Mikoto (and getting called a pervert in the process), and tends to get jealous if someone else gets her attention; this unfortunately happens to be Tōma since he has caught the attention of Mikoto for various reasons. However, it's been shown on few occasions that she is genuinely in love with Mikoto, even allowing herself to get severely hurt (see Tree Remnant arc) in order to help Mikoto. She is classified as Mikoto Misaka's best friend. Her power is instant teleportation, which allows her to teleport herself and anything in her possession as long it weighs under around 130-137 kilograms to anywhere in a radius of around 81-85 meters. She generally carries a strap of needles around her leg that she can teleport to pin down enemies. One disadvantage of her power is that she has to concentrate on where she, the object(s), and/or person she holds would be teleported to, for any disturbance in her concentration will make her powers useless.

(Source: Wikipedia)