Emperor of Mankind from Primitive Times

A soul that has been alone in darkness for countless years and has even forgotten its own name. An era that is devastated, obliterated, and constantly facing destruction. "Nameless" became the reincarnation of this era. He became a human again and again until the flame named interest ignited in his heart. In the primitive era, extraordinary power was extended to the entire race and a path called a profession was created. In the era of unified empire, the true meaning of faith was spread. In the future filled with stars, take your own country to an unreachable peak. Humanity will also be reborn from the fate of constant destruction and move towards the crown of all worlds. (There is a transformation plot, and the gender of the protagonist changes in each volume, but there is basically no emotional line, and absolutely no love line.)