Hyouka Kazakiri

She is Index's first "friend" in Academy City. She is gentle but shy. Not much is known about her aside from the fact that she was an overachiever at Kirigaoka Academy for Girls (霧ヶ丘女学院, Kirigaoka Jyogakuin?), according to Aisa. Her ability is Counter Stop (正体不明, Shōtai Fumei?, "Unknown Identity"). Details about her level are unknown but it could be high, since it was mentioned that she was among the top psychics in the Kirigaoka Academy for Girls. It is later revealed that she is not a human at all but instead an algorithm of the psychic's AIM with a conscious. The nature of her being leads her to be indestructible, as she can recreate any damage done to her body and lift objects several times her size.

When not physically manifested, she exists in a realm called the Imaginary Number District which she calls 'the city of shimmers', a hidden area within Academy City. (Source: Wikipedia, edited by KazeFalcon)