Kazakiri Hyouka (風斬 氷華 Kazakiri Hyōka?) is Index's first "friend" in Academy City. Not much is known about her aside from the fact that she always had top marks at Kirigaoka Girls' Academy, despite never actually being seen by anybody, according to Himegami Aisa, and is referred to as the Key to the Imaginary Number District. She is the conscious form of the aggregation of the AIM Diffusion Fields of espers in Academy City, the Imaginary Number District.