The Empty Box and Zeroth Maria, Vol. 3 (light novel)
Utsuro no hako to zero no Maria
Bok av Eiji Mikage
Kazuki and Maria have been trapped once more, and this time, it's someone they never would have thought was a User. When the trial they face turns out to be a role playing game, it'll be the greatest test of their ability to keep a secret and stay alive until the end!