Edit: Chapter 1020 reveals that Yamato has the Inu Inu no Mi, Model: Okuchi no Makami.
I love how Yamato has been causing problems for Kaido since Oden’s execution. Even with being shackled, imprisoned to one Island for decades, and beaten each time after a challenge, Yamato never once conceded to Kaido’s plans for him. Rather Yamato’s actions were a constant reminder to Kaido that he didn’t defeat Oden and that he isn’t as sovereign as he would like himself to believe. Kaido confirms that Yamato had consumed a Devil Fruit that he viewed as valuable, one he didn’t intend for Yamato to eat. The visual appearance of Yamato’s current form may give us some ideas as to what the Devil Fruit is.
I may have been wrong about the Nue Devil Fruit (as it is already a non-cannon Devil Fruit) but the chimera nature of the Beast form Yamato takes may still apply to the Devil Fruit Yamato has. The appearance of Yamato’s form does convey a Mythical Zoan variant, one resembling a Qilin/Kirin or some variation of Faun. It does look divine. But could it be another type of Devil Fruit that gives the appearance of a Zoan form? Oda-sensei omitting to show Yamato initially transform and his full Beast form is quite suspicious. Oda-sensei jumped straight to a Hybrid looking form, why? To make the readers presume the Devil Fruit is a Zoan type perhaps? Could Yamato’s Devil Fruit be a Paramecia type or a Logia type? A Devil Fruit that allows some form of shape shifting. It could be possible. If Oda-sensei wanted to introduce a special variant within the Devil Fruit sub-classes, he could.
I don’t believe the Devil Fruit Yamato has is a Logia due to the lack of elemental features present when Yamato was attacked by Sasaki’s group, although in that situation, Yamato could have been consciously taking the hits so that Momonosuke and Shinobu weren’t hit. Or it could function similar to the way the Yami Yami no Mi functions.
The Devil Fruit situation of Yamato accidentally eating it due confusion over it being food was hilarious. Kaido doesn’t strike me as someone like Teach who would go hunting for Devil Fruits as he hasn’t been shown doing that actively (I don’t expect him to have gifted the Tobi Roppo their powers before they conceded to him and chose to follow him – the Tobi Roppo likely had their Devil Fruits before joining the Beast Pirates). So Kaido going out of his way to acquire the Devil Fruit Yamato consumed is very curious.
Kaido specifically mentions his annoyance at Yamato for consuming the Devil Fruit he worked hard to acquire. That Devil Fruit was never intended by Kaido for Yamato to consume. Who did Kaido wish to consume it or did Kaido have other plans for it? Could Kaido have intended to trade the Devil Fruit for a more valuable reward? Kaido has been an active player in the Underworld (buying Caesar’s weapons, engaging in trade with Doflamingo via Wano crafted weapons and SMILEs and having his subordinates follow the Underworld broadcast), so it wouldn’t be surprising for Kaido to engage in Devil Fruit trading – maybe with the Blackbeard Pirates? Could Teach have wanted the Devil Fruit Kaido had acquired which Yamato consumed for his third Devil Fruit power? Teach already has a Logia and Paramecia Devil Fruit power. If Teach is to consume a third Devil Fruit, it does seem set-up to be a Zoan Devil Fruit, but does it have to be? Yamato’s Devil Fruit is likely a Mythical Zoan variant so that could be why Kaido acquired it. Kaido may have wanted to bargain the Devil Fruit to Teach in exchange for something valuable to him be it and item or a service. If Teach did want the Devil Fruit Yamato consumed, it would create a connection between Yamato and the Blackbeard Pirates once Yamato joins the Straw Hat Pirates. Alternatively, Kaido could have acquired the Devil Fruit for one of his core subordinates to consume.
Could Kaido have acquired the Devil Fruit from the Red-Haired Pirates during the Marineford War incident? Kaido was stated by the Marines to have targeted Whitebeard while the Whitebeard Pirates were moving on Marineford but Shanks intervened to stop Kaido. Shanks eventually arrived at Marineford to stop the War. Why did Kaido back down? Was his move on Whitebeard all a ruse to draw Shanks out? And did Kaido intend to steal a Devil Fruit Shanks possessed based on the Beast Pirates intel? Shanks has acquired Devil Fruits before (Gomu Gomu no Mi), which was recently revealed to be stolen from a World Government ship, so there is precedent in place to support Shanks possessing another Devil Fruit. Once Kaido stole the Devil Fruit, he left and let Shanks proceed to Marineford. The efforts Kaido went through to draw Shanks out could be the hard work Kaido mentioned to Yamato when acquiring the Devil Fruit. If this is the case, there could be a special reason for why Shanks possessed the Devil Fruit and why Kaido stole it. Yamato possessing this Devil Fruit would create a connection to Shanks, another Yonko that Luffy will meet again (Luffy’s Oden so to speak).
Like the New Generation, Yamato is one of the few characters Oda has shown to continue to stand against a Yonko even after being defeated and overwhelmed. And the reason why stems from his core convictions like Luffy, Zoro, Law, Killer and Kid (probably also Drake once we get more focus on his goals). These New Generation Pirates will not bend and compromise their beliefs. Yamato has expressed to Kaido, the chains Kaido placed on him weren’t the only things keeping him in Wano. Yamato had also resolved to fight for Wano, to see Oden’s will through. By transforming, Yamato has conveyed his resolve. Really looking forward to the next chapter.