Atrium no Koibito (Volume)

is the first volume of the Atrium no Koibito light novel series, written by Shinjiro Dobashi and Illustrated by Ryo Ueda. It was released under the Dengeki Bunko Imprint in May 2011.

Synopsis
The virtual world "Tokyo Sphere" closed for some reason. Maeda, a high school student, is consulted by Haruka Aohara, an idol in a class who usually does not exchange words, about her existence. Tokyo Sphere admission ticket and a large sum of 1 million yen ── After that, Haruka, who wants to relentlessly investigate Sphere, invites several students besides Maeda to establish her circle. Is the ticket a welcome "invitation" for Maeda, or ── !?

(source: Dengeki Bunko Official Website - Translated)