This world is home to a Demon Lord. The Demon Lord and the demon race are humanity's sworn enemies, beings to be reviled. Thus, they waged war for the annihilation of the demon race.

One day, humanity discovered an ancient text in a ruin. It was said to contain the following words...

『A Hero from the Unseen World shall strike down the Demon Lord.』

What could the Unseen World be? Researchers, for the time being, concluded that the Unseen World was likely an 'otherworld' (異世界), and the kingdom then commenced a search for this hero.

This story follows a certain magic-user in such a world.

This work is also published on 『Kakuyomu』.