The Universe’s Last Martial Artist

When the "Great Convergence" merged Earth with a ruthless Murim realm, humanity survived by unlocking magical Classes. Min-jae, however, awakened the only non-magical, pure Martial Arts class—deemed the weakest, most obsolete path in a world of fireballs and lightning strikes. After dying a pathetic death as a meat-shield in a high-level dungeon, he regresses ten years to the day of the Convergence. This time, he isn't alone. He has a glitched "Overmaster System" that rewards him not for using mana, but for breaking his muscles, mastering breathing techniques, and executing flawless, old-school martial arts. Starting from a frail, broke teenager, Min-jae begins his relentless grind to prove that a perfected fist can shatter any magic. — Description from novelcodex.org