Hi Mewtwo!
Ash here, so, it's been a while and a lot has happened, I know that you don't want anyone disturbing you so I haven't been telling you most of it, but this is really a special case.
So, first, I really need to tell you that it turns out my dad was a Pokémon, and since something that happened a couple of months after we last met I'm one now too! I, hope that doesn't mean you don't like humans any more, though, some of my best friends are humans and my mom's still a human and stuff.
But, the really important thing is that we met someone just now who was making artificial Pokémon, and one of them – the only one who was really a person – was a Mew, and he hated that about them.
He just wanted the artificial Pokémon he was making to be for battling, nothing else, so he called Mew a failed experiment.
And because I'm a Pokémon now and I've got powers to do with making things I made Mew into a real Pokémon. And, I guess that means that I'm Mew's dad, or something, but Mew's worried about if they're real. I told them they were but I think they still need help to believe that, and, I'd be no good at teaching a Mew how to be a Mew anyway.
So… I really hope you can help Mew out. Because it seems like you'd have some ideas about that.
I hope this doesn't disturb you. It'd be nice to visit some time but I wouldn't want to do it without asking you first.
p.s. Oh, I should say, Mew is the Mew who delivered this letter to you! I told them where Mount Quena is and what you look like.
You can probably reach me through Professor Oak or something, if you want to send a message back. The same goes for in case Mew doesn't know where to find me.
AN:
Yep, it's an epistle. About an apostle, possibly.
Mewtwo's probably going to be quite surprised.