Why Nobody Remembers My World?

[Ojisama]

Coming in July.

War between the five races on earth - the humans, the "Demonic Race", the "Wild God Race", the "Spirit Race" and the "Phantom Beast Race"- has ended in the victory of humans.
It is said that "Prophet Sid" had sealed the other four races in the black pyramid now called "Crypts".
Kai's job is to watch the crypts and make sure that there is no change. He is also training to save humans when the other races break the seal and come back to this world.
The crypts looked quiet today...but after Kai felt the world bending in front of his eye...everything changed.
"World Rebirth" was activated...!!
Now Kai is in a totally different world where no one knows him. But he remembers everyone!

[Expendable]

Reminds me a bit of Midnight at the Well of Souls by Jack Chalker. Basically, an advanced alien race asks itself "what did we miss?" and decides to use their technology to create a universe to put on top of their one, and to turn themselves into various unique races to populate this simulation. Years later, a university expedition runs into one of their worlds with a working gate portal to the Well of Souls.... A frieghter captain picks up their distress call and diverts to the planet with his passengers, and they wind up being transported to the center of the aliens' universe.

And yes, humanity is one of the races the aliens created.

[Ojisama]

Reminds me a bit of Midnight at the Well of Souls by Jack Chalker. Basically, an advanced alien race asks itself "what did we miss?" and decides to use their technology to create a universe to put on top of their one, and to turn themselves into various unique races to populate this simulation. Years later, a university expedition runs into one of their worlds with a working gate portal to the Well of Souls.... A frieghter captain picks up their distress call and diverts to the planet with his passengers, and they wind up being transported to the center of the aliens' universe.

And yes, humanity is one of the races the aliens created.

Have you read the sequel?