The speech between Marco and Big Mom in Chapter 992 confirmed 3 things:
1-Kaido and Yamato are not humans: after being called a “creature” by the narrator, and a “thing” by Big Mom, Kaido even has natural horns from his head which Yamato inherited.
And now add all that to Marco straight up calling him “ogre” in a matter-of-fact manner. IDC what anyone says, there’s more canonical evidence to support Kaido and Yamato NOT being humans than there is to support that they are.
2-Big Mom still has something up her sleeve: According to Sengoku, the Rocks Fleet weren’t exactly known for their camaraderie and turned on each other quite often.
Let’s also note that Kaido and Big Mom’s ambitions are completely the opposite. Now add that together, does it still make sense for them to be allies? Also, given that the World’s Greatest Pirate Alliance was in fact, her idea, and, how she clearly has not lost sight of her goal. She obviously intends to betray Kaido eventually.
3-The other Whitebeard Pirates aren’t coming: I’m no longer looking for someone like Jozu or Vista to show up after how the talk between Big Mom and Marco closed out.
Yes, it’s true, Whitebeard did order his men to “back up Strawhat from now on.” But that was back when they were still his subordinates and when he was alive. Marco said it exactly how it is “Do you think Pop’s voice still binds us to his will? Everyone who’s left is now free.” And Big Mom could not have said it better herself. “Dead men give no orders.”
Which is true. Marco and Izo might be all we see regarding the Whitebeard Pirate remnants.
*Theory by Extinction17
