Utsuro no Hako to Zero no Maria

Utsuro no Hako to Zero no Maria (空ろの箱と零のマリア) is a Japanese light novel series by Eiji Mikage, with illustrations by Tetsuo. The first volume was released on January 07, 2009. Currently, There are 4 published volumes. all published by MediaWorks under their Dengeki Bunko label.