We all die once.
It's just that everyone's memories are locked into the depths of the subconscious.
Horror dungeons are opened one after another, limited resurrections, bone-eroding auditory hallucinations and bloody death flashbacks constantly tear apart sanity.
We thought we just accidentally fell into the trial, and we desperately tried to find a way to return to reality.
Little did he know that the whole world was the tomb of death that he had personally restarted in order to reunite.
Concept: human nature