Hoegwijaga Da Mandeureojum

Lee Sehun is a master blacksmith who was supposed to save the entire world before its destruction—if only he had realized that sooner. As Pandemonium and its Demon Gods drown the world in the Sea of Annihilation, he hears the mysterious sound of crashing waves that usually guides him and decides to make his last creation before doing the unthinkable... But then, he awakens 31 years in the past! And this time, he must remaster his craft and use his creations to stop the impending apocalypse. (Source: Tapas) Note: Includes one extra chapter.