[Manga] Naze Boku no Sekai wo Daremo Oboeteinai no ka
What happens when you mix magic and technology, then cause an apocalypse by rewriting major world events? The MC basically gets isekai'd in his own world, as if he was from the wrong time stream.
"Why does no one remember the true world?!"
The era when the great race of the five tribes competing for hegemony on the ground ended with the victory of mankind led by the hero Sid. However, that world was suddenly "overwritten" in front of a boy named Kai. In the rewritten world, Kai saw the scene where humans lost the five tribal wars because of the absence of hero Sid. Here dragons and demons dominate the ground, and Kai is a forgotten existence from all human beings. However, after encountering the mysterious girl Rinne, Kai decides to break this rewritten destiny. In a world without heroes, he inherits the hero's sword and martial art to challenge the mighty enemy races who reign supreme.
I was a bit surprised at the quality of manga and the story seems to be captivating. A light novel of this exists as well, but I was unable to find it on Novel Updates.
Someone has also requested the light novel, for reference: