You know what, I'm still holding out hope that its "Ash" appearance is just a demo-exclusive placeholder, and in the actual games, it'll have an appearance entirely based on your trainer's customisation.
It's kinda clever how they implemented Ash Greninja though - you can only get it in the demo, which isn't canon to the game (it's like a side quest) which matches how the anime isn't canon to the games. And it says on the site that a special person gives you the Greninja, so will Ash appear in the demo? I gotta admit though, it's still pretty strange that you can use Ash Greninja when you're not Ash.
Ash is in the game world. If Samuel Oak is a cousin to the popular Oak then why can't Ash be included? Also each pokemon game timeline is different. Meaning it could be Ash was the first person to ever "evolve" a greninja. Then it became the natural way for Greninjas to look upon obtaining such a form.
The official site kind of implies that Ash is in the game, actually... and that in the demo, we are gifted it by someone who is not Ash, but got it from him, I guess? Idk.
That's why I never look at the thumbnails. I just don't look at them and click on the video.
That's actually what I do too, but today I wasn't watching it on my normal laptop, so I managed to get a glimpse of it
They always come out while I'm at school for me (pretty much always during PE) so I watch them like almost an hour after they come out during community time on my school iPad. Then I just spend my study hall quietly analyzing it. XD