In the year 199X, mankind collapsed civilization by its own hand. To atone for their mistake, people built a tower high in the sky. They hoped that their hearts would not be ruled by demons again. One hundred years later, the earth is ruled by monsters, and the people are living in fear, but they are still living together, dreaming of the return of peace. The basis for this hope is the legend of a savior that has been passed down from generation to generation.