Colosseum (Volume)

is the first volume of the Colosseum light novel series, written by Shinjiro Dobashi and Illustrated by Yukiko Horiguchi. It was released under the Dengeki Bunko Imprint in April 2015.

Synopsis
"You will kill each other at the Coliseum behind the door." When the girl woke up, there was a space she had never seen. She is given a pistol and knife and forced to kill each other. A ruthlessly organized death game. Of the 30 people gathered, only one can survive. Yuto Hagiwara, a high school student, learns from an app that he picked up on the internet one day that a death game called "Coliseum" is being held and that Io Tsukishima, the central figure in the class who should have committed suicide, is participating in it. Yuto finds out that she can support her from outside using her app, but tries to clear the game with her classmates ... The 30 people gathered in common point out the terrifying truth to Yuto! School survival suspense that cannot be turned away!

(source: Bookwalker JP - Translated)