Genta Naito finds himself in a new world after being summoned by a group of mages to help them against the demon lord's destruction. Unknown to Genta, there is more than one demon lord in this world, and many reincarnations before him are pursuing their own paths, making it harder for the inhabitants to survive. As he uncovers the mystery behind the numerous summons that brought people here, he also learns about an ancient battle that has been ongoing that may be bigger then He Realzies