Tada no Murabito no Boku ga, Sanbyakunen Mae no Boukun Ouji ni Tensei shite shimaimashita - Ch. 9.1

[ScryedParadox]

...he's a reincarnator, right?

If you're talking about the MC, yes.

But not from Earth. But from the future of that same universe. Although he has just changed the timeline completely.

From what I recall reading, the MC is the only reincarnator. And I have read fairly far into the story. For example, I know what happens to the shit prince in this chapter and how things ends for him. And what happens to the other princes too.