...Wow. Mind-blown
Guess that rules out Kaidou as a natural born Dragon then. But, really, to think Oda left readers a big fat hint during the intro to Wano with that reference to Carp that scale the waterfall becoming Dragons, based on real-world Chinese and Japanese myths. Colour me stupefied.
Liking the idea that perhaps Kaidou got what amounted to a seemingly 'lousy' fruit (turns into a fish) but somehow worked his butt off and evolved it into the Dragon form, kinda like how the legends of the Magic Carp where the Gods change the brave and strong-willed Carp into a Dragon in tribute.
Still doesn't quite explain why BM refers to him as a 'thing' though or thereof. This gives an explanation as to his fruit, not what he really is, yet. I mean, it's an awesome talking point sure, but don't think this is all there is to Kaidou. It'd be like saying all there is to WB or BM is their fruit powers, when that is not true. BM's durability and strength came before she gained her fruit - a twist of nature, a biological aberration so rare it's nearly unique.
Yamato and Ace...hmm. Still don't care either way whether she joins or not. Rather hilarious that Ace intended to kill Kaidou but he wasn't home.
BM wanting Nico Robin while Kaidou remarks on Pudding feels like they are both assessing each other's assets here. At the same time it brings them up to speed on the urgency of deciphering the Phoneglyphs. Now readers know the Yonkou are actively loking for the means to unlock the secrets of those stone carvings. The story is beginning to revolve around the core plotline of finding Raftel and the One Piece now.