Shinwa Densetsu no Eiyuu no Isekaitan (Light Novel)

Ouguro Hiro was once summoned into another world called “Aleitia” where he conquered all nations around his own to form a great empire and was celebrated as War God Alus. Following which, Hiro decided to give up on everything, losing his memories there as price for returning to his own world. There, he lived in peace once more, but was summoned to Aleitia again due to a trick of fate. —This time, it was the Aleitia of a thousand years later. His past glories were now myths and the boy known as the “Dual Black Hero King” in the past now begins another legend!