RTA Sousha wa Game Sekai kara Kaerarenai

Our protagonist, the RTA speedrunning king of the game "Another Verse", suddenly starts feeling sleepy in the middle of practice. When he wakes up, he hears the familiar opening of "Another Verse" playing right before his eyes!? In this god-mode environment where everybody is moving quicker than usual, you have to speedrun! Clear the game world faster than everyone else! Use every trick and abuse every bug to fight, in this "fastest" Isekai fantasy!! (Source: Monthly Comic Flapper, translated)