Hey, a new canon! The Mii properties deserve more love, I think.
The agents seem fun. I don't know anything about Dream Girlfriend, so I hope to learn more about Paye's history in the future. I like the concept behind Null quite a bit; a non-aggressive vampire in a middle-aged body is quite funny! (And I love that he got the vampire costume as a disguise.) I am concerned that he seems to be in the PPC against his will, though; that's not something the Flowers do. I'd like if future installments show that he is still able to see his family at will.
You did a good job of explaining all the ways the Word World was fuzzy and undescribed, but you also left the agents' RC very undescribed in the opening scene. I know most RCs are pretty interchangeable, especially before the agents have properly moved in, but as it is, it's hard to get a sense of where the agents are in relation to the rest of the room there.
Some minor errors:
There are a couple lines of dialogue that are missing the ending quotation marks:
"He's a mischievous little one.
"or we could let them integrate with the canon.
And this here is a run-on sentence:
Paye couldn't have figured it out herself without looking at the Words, no matter whose POV it was, the world was just as generic (and in the same way) as before.
To me, the most logical fix would be switching the comma after "Words" to a period, and letting "no" start a new sentence, but there are probably a few different ways it could be changed.
—doctorlit was going to point out a comma substituted for a period too, but when he scrolled back to find it, the comma turned out to be a crumb on his computer screen