I.d.

is a Japanese light novel series written by Gakuto Mikumo, with illustrations by Kazuo Miyamura. The series began publication on November 10, 2003 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
Formula. It is a willing "magical power" that sleeps in the depths of human consciousness. In exchange for giving the host a great deal of power, there is always the danger of runaway . A high school student, Rui Inase, was once one of the children who was educated to manipulate their special abilities at a cram school called Kakuha Juku.

Six months after the collapse of the Kakuha Juku due to a mysterious big fire. An envelope is delivered to the person who lives as an ordinary high school student.

It was a copy of a newspaper article reporting the incident of the bizarre murderer "The Severer" that occurred four years ago.

Then, people are killed one after another in the closed school as if to reproduce the case. Can Sui protect a loved one from a criminal who manipulates the same magic ...?