The Regressor Makes Everything

Lee Se-hoon, the blacksmith of humanity's final suicide squad, battled against the demons until the very end, leading to mutual annihilation and the world's destruction. At the time he ended his own life, overwhelmed by the absurdity, he shouted, "what is this?" He found himself back in his days as a trainee at the hero training institute Babel. A new chance presented itself. He would do whatever it takes to secure victory. Anything!