Kyouko Akaza is an ordinary high school student until a fateful encounter that changed her life forever. She was transfered to a place called the realm of eternals and there she met a man Shirou who asked her if she wishes to abandon everything from her previous world and live in another world. After agreeing to be sent to another world Shirou told her. "In that world you must defeat the demon king." And afterwards she was transported to a new world filled with magic and liveliness. In this world humanity faced a threat that called the demon race. A force that humanity can't possibly on their own. Despite being the largest in numbers amongst all the other races. Humanity will soon face extinction due to the war. When the demon king declared a full-scale war against humanity. One by one the countries ruled by the humans fell and became part of the demon king's territory and as his land grew larger and larger humanity was being force into a corner and Shirou sent Kyouko there to help humanity deal with the situation. Can Kyouko defeat the demon king or will humanity fall into ruin and chaos?