Isekai Saiken Keikaku

A thirty-year-old Japanese city clerk named Eiji is summoned to a fantasy world that has already been saved by another hero, also from Japan. While the previous hero brought elements of modern Japanese society into the world, Eiji's mission is to undo that influence and return the fantasy world to its original state. The world is now on the verge of collapse due to the changes introduced by the earlier hero. Eiji is not called as a hero but to correct the damage caused by the infusion of modern technology, ideology, and social structures. His task is to rebuild the world as it was before these changes took place.