This is the first Well of Souls story.

Nathan Hunter, as well as five hundred other seniors at his high school, found themselves pulled into the deadly game in an alternate dimension of their school, where they had to survive against increasingly tough monsters while completing a series of Challenges as their numbers continued to dwindle with no end in sight. With no way off the property, nor any way out of the alternate and back to their real dimension, Nathan and his classmates battle for survival in the hopes that eventually, they will be freed from the game.

Warning: Things will get repetitive at times, particularly after Arc 1. The reason for this becomes clear in the first couple of chapters of Arc 2. It is simply the nature of the lives they lead.