Sumigahara Uguisu no Ronshou

is a Japanese light novel series written by Shiki Kuzumi, with illustrations by Katsuki. The series began publication on August 10, 2009 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
The girl named Uguisu is strange. I always stay in the library and don't show up in the classroom. However, it is the first time for a twister that he has never scored anything other than a perfect score in the exam. For some reason, Yuzuru had a strange relationship with her.

A strange request comes to a strange person. Saima Kiryu, a genius mathematician, is a magician-I want you to question the truth. Thus, Uguisu and Yuzuru went to the Kirinkan where Dr. Kiryu was waiting. However, the next day, Kiryu was a headless corpse. Limited suspects fall into a strange situation where everyone is innocent !?