Aka no 9-ban Reiju (Volume)

is the first volume of the Aka no 9-ban [Reiju] light novel series, written by Akira Aihara and Illustrated by Kazuoki. It was released under the Dengeki Bunko Imprint in January 2010.

Synopsis
"I'm Red No.9. I'm looking for a player to bet on me urgently." A mysterious message I found on my longing classmate's blog. A mysterious game opens!

(source: Bookwalker JP - Translated)