Oono Akira, a working adult that can be found anywhere, was transported to a different world while logged into a character known as the "Demon Lord" in a game he manages. There, he meets a girl with a disabled leg and they begin to travel together, but there's no way that others will leave a "demon lord" with such overwhelming strengths alone. While being targeted by countries and saints that are trying to subdue the demon lord, they cause turmoil wherever they go.