Atrium no Koibito 3

is the third 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 February 2012.

Synopsis
Tactics Tokyo was successful and the Sphere world was steadily revitalizing. However, Atsuto Maeda was involved in "Mysterious Phenomenon"! He finds himself lying on the bed every night. The world was clearly different from my own, nor was it a sphere world. It feels like you're in a dream world ... Another world memory that cannot be carried over, and survival for survival that will occur. What does that phenomenon show? The third popular series!

(source: Dengeki Bunko Official Website - Translated)