It is the year 20XX, and a terrible monster attack has been brewing for a long time. Monsters have started to emerge from the ancient ruins, and the only one who can fight them is the hero that is summoned by the people.

But the people only know him as the knight who fights monsters. The hero has no name, no memory, and no knowledge of the world. All that is known about him is that he has a sword and that he fights monsters.

But the people need to know more about him. So they send him to the ancient ruins to find the secret of summoning heroes. There, he meets a wizard who tells him the secret of summoning.