, also known simply as , is a Japanese light novel series written by Yashichiro Takahashi with illustrations by Noizi Ito. ASCII Media Works published 26 novels from November 2002 to November 2012 under their Dengeki Bunko imprint. The story focuses on Yuji Sakai, a high school boy who inadvertently becomes involved in an age-old conflict between forces of balance and imbalance in existence. In the process, he befriends a fighter for the balancing force and names her "Shana". The series incorporates fantasy and slice of life elements into its tale.