Tinfoil hat time I guess. Hopefully not too rambling of a theory that might get destroyed in a month or less.
And spoiler warning? It's nothing too bad I think, but a warning anyway.
Tanuki and the possibility of a character being able to change shape was brought up before in maybe the day 15 update with Orlando and Dean both mentioning knowing someone that could change shape. It was confirmed by Orlando as being real in this one. I've had the theory of a shapeshifter being on team bad for a while but until now it didn't have any actual evidence beyond a couple quick lines of dialogue. But it would make sense there's more than just Jack and Dom in the woods.
Some of the murders could be blamed on this person as well. It wouldn't really be unusual to see a friend walking around the mansion for instance, you might not even take notice of them closely enough to see it's not really them at all. If they know about the secret passages, well "Benson" coming and going through them wouldn't really raise any alarms. And I mean someone snuck in and stole stuff out of Oswins lab.
Then we have Orlando's vision. "Dean" is seen laughing at Dave's body, either this is Dom wearing Dean's jacket or it's someone that just looks like him.
At some point over the next in game week, Dave will leave the mansion and go into the woods again. I'm just so curious as to how that happens with him being too scared to even step outside alone right now. Just, if he were following a "friend" or someone he trusted... he could be led into danger really easily. Path C/D proved that much already. But then the password itself to get that vision may imply he'll go willingly? Of all the deaths his is the one I'm most... excited sounds bad to say because I like Dave, but I'm looking forward to that story bomb detonating.
And I really recommend paying more attention to Roswell. His route and character may be my second favorite overall (after Tyson) just because of his dialogue and interactions with Dave. Like with knowing about the shack in the woods before going into the forest. Sometimes it feels like he's either experiencing bleed over from other timelines (the shack/cabin seems to be the place he and Orlando will find Dave eventually) or just outright knows about it already. Also what happens on path C/D, he's the first for some reason, then his interaction with Thanatos on path B, how he acts in the latest update when Dave wants to check up with Oswin. I just find him fascinating and am really looking forward to his update next month.
As for the handshake/promise... Roswell drops some fairly dark hints about what's potentially going on with him. His focus on death and accepting it at such a young age, how he reacts to finding the medal on his route, Oswins research in general, what the greenhouse plants are mentioned to be useful for, the fact he doesn't really survive any ending, etc. So the promise he makes and Dean's reaction to the contents of that conversation, Roswell worries me to put it lightly.
But as of right now, I don't feel comfortable second guessing or being suspicious of any of the main cast.
Though... in fairness I may just not be a good judge of character since I trusted Jack at first.