Naze Boku no Sekai wo Daremo Oboeteinai no ka?

Briefly Read Naze Boku no Sekai wo Daremo Oboeteinai no ka? Manga. 

People often do not appreciate what they consider ordinary… Especially mankind has learned to treat the world peace with care. Time and again, wars flare up, and people lose the battle for battle. All races are at war with each other, and there are no winners and there will be no winners, because in any confrontation with the use of weapons, there are many deaths… After the defeat of humanity, the Earth was captured by mythical creatures. Demons with dragons settled on once fertile land and Kai all forgot. But the hero met Rinna, and now his goal is to rewrite fates. Now he has to stand up against the ruling evil dragons and go through the hellfire of demons to change the course of events and return the world to the planet.