YOIO! (YOU ONLY ISEKAI ONCE!)
Connected to Japan via wormhole, the Holy Eldant Empire exists in a parallel fantasy world, where Shinichi has been spending his time as an otaku evangelist. He’s learned that this world is actually a far-future version of our own, and now it turns out instability in the wormhole might threaten the ability to go to modern Japan and back: everyone who’s been sent here could find themselves stranded on an island floating in time.
Shinichi and his friends are instructed to leave the other world behind, but Shinichi’s heart is here, and it won’t be so easy for him. As if that wasn’t enough to worry about, he suddenly finds himself confronted with a major threat to both his world and this one… or is that this world and his one? Wait, which world is which? The point is, everyone’s in a lot of trouble! And wait… What’s this about a final countdown? Huh?