RTA Sousha wa Game Sekai kara Kaerenai - MangaDex
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Our protagonist, the speedrunning emperor of "Another Verse", suddenly feels sleepy in the middle of practice. When he awakens, the familiar opening of "Another Verse" is playing right before his eyes!? In this godly environment where the body is moving better than usual, you have to speedrun! Clearing the game world faster than anyone! Abusing bugs to fight, the "fastest" Isekai fantasy!!

MC is a speedrunner that got isekai’d into the world of the game he played. As soon as he reached the isekai, he immediately speedrun thinking he’s in a lucid dream. And he managed to defeat the Demon King in only 30 minutes since his summoning. But… I’ll leave the rest for you to read.