I Became a Dungeon Prisoner Trainer

Reincarnated into another world without a single cheat, I scraped by as a mercenary until I was captured by a demon army executive. 'So you're that good? Follow me to the training room.' To survive, I accepted the role of a trainer for human prisoners. But failure means death—and a regression to the instant of my last climax. Every time I die, I return to that exact moment.