Let them rest
It was an old myth, but it was still popular among old and young. No one knew if it had really happened, however. But isn't that how myth's work? But alas, enough chitchat for now. I am only here to tell you this myth... this myth that is not a myth after all, but the truth spoken by millions of mouths.
Years ago, there was a boy. His name was Minato Arisato, and he is the one who failed to stand up to prevent the World's end. Of course he had tried, but somehow he faltered and fell – and eventually died in the process without reaching his goal.
However, two of his Persona's, manifestations of his psyche, had somehow managed to snatch his memories to recreate humanity. Every person he had seen, every place he had been or seen would be repaired. Life went on, as if the World had never seen it's fall.
But, because he had still memories of awful things – those were recreated too. The Dark Hour, Tartarus and Nyx remained, but the threat of Nyx wasn't able to resume it's destruction as people somehow learned of their mistakes, even though they didn't know they had made them. They wanted to live. And thus Nyx was never contacted and appraised to this world.
However, years and years later, the Dark Hour still affects people and puts fear in their heart. But there also were humans who fought the Shadows. Alone, because they wanted to snatch back their mother from the Shadows, in a couple because they were missing someone or something, or together in groups because they wanted to end all of this.
They never had belonged in this world, but somehow they did – their ancestors had somehow been recreated in this new World after all while they did not belong. They had adjusted very nicely, though.
We, you as the reader and I, will follow these descendants. Their names shall be unknown to you until they decide that you are trustworthy enough to entrust their identities to.
Welcome to the world of Persona.
But remember... you have to die someday.