Regressor Instruction Manual follows an ordinary man who gets dragged into a deadly fantasy world where only the strongest survive. Unlike typical heroes, he is not powerful or gifted—his only advantage is his extreme survival mindset. He soon realizes he is a “side character” in a system where regressors and powerful awakeners dominate. Using manipulation, strategy, and psychological tactics, he tries to climb the hierarchy, survive deadly scenarios, and gain control over stronger players by any means necessary.