Chikashitsu no Akuma: Akuma Detekuru

is the first volume of the Chikashitsu no Akuma light novel series, written by Taro Achi and Illustrated by Kurito Muto. It was released under the Dengeki Bunko Imprint in December 2004.

Synopsis
Childhood friends Takao and Elina are in the second year of junior high school. One day, the two men who repeat fights every time discover a secret basement in an old school building that is no longer in use. A magic square is drawn there, and on the old desk there is a magic book and something that seems to be ... And the devil that appears aims at the lives of the two !? Men and women placed in extreme conditions tend to fall in love-when that story is written by Taro Achi ... You can laugh even with a promise. A little pounding romantic comedy.

(source: Amazon JP - Translated)