What If A Otaku Become The World Savior?

In the World of Erden which lived by Seven races which is humans, Elves, Half beasts, Orcs, Demons, Dwarf and Fairy creature once live in peace and co-existing with one and another.(Except for demon race) But, out of nowhere the unknown race called them self as The Ancient rise and claim to invade World of Erden as Or...