Kamisu Reina Series

is a Japanese light novel series written by Eiji Mikage. The series began publication on December 10, 2005 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
She is [I]'s best friend. A close friend who belongs to the track and field club and is always out of school with a different class. She hates killing [I]'s family. I won't forgive her. I've killed my family and still don't forgive her alive! She is a member of [I]. To erase humanoid energy ... A companion who fights together to save the world's crisis. She is [I] ... She always has a funny smile on her face. What is she for [you] ...? A slightly mysterious story spun by people around the mysterious beautiful girl Reina Kansu ....