Great chapter, one of the longest theories has finally been confirmed to be right. Dr. Tsubasa is AFO doctor. Now that doesn't confirm that Deku had a Quirk stolen from him, but I think it makes it extremely likely that he did.
At very least it confirms that the Flying Nomu that Stain killed was mostly likely the Doctors Grandson, the one we saw gang up with little Bakugo to fight Deku. Which is very dark stuff, that he would do something like that to his own Grandson.
Also there was also the theory that the Teleportation Sludge stuff wasn't a AFO Quirk, but the Doctors Quirk, and that seems to have been confirmed as well.
Now once we learned that Deku had access to 6 other Quirks, which would bring his total of Quirks he could potentially use up to 8, (The brothers Quirk, Stockpile, and the 6 others = 8). I thought Horikoshi being such a big fan of Naruto that maybe Deku would ultimately have access to 9 Quirks, a nod to the 9Tails. And I could see this happening.
Now a big thing about the Doctor and the fact that AFO most likely uses that as opportunity to steal Quirks, and if Deku had a Quirk stolen? Then that either means Deku Quirk wasn't a Physically seeing Quirk like making Fire, or AFO can somehow tell what a persons Quirk is just by looking at them?
Either way very interesting stuff.