The battle between father and child is about to take place, as Kaido and Yamato lock horns (literally). The Emperor of the Sea’s child desperately wants to break away from the controlling parent and sail the seas with Monkey D. Luffy. Meanwhile, Kaido, for obvious reasons, refuses to accept this desire.
As a result, Yamato has revealed her Devil Fruit powers for the first time, with some fans taking to the internet and theorizing that her powers are sourced from a Smile Fruit. Remember, Kaido is the mastermind of those fruits production and many of his crewmembers have eaten Smile Devil Fruits.
and she speaks of eating the fruit as a last resort before starvation. This could mean that she was aware that the fruit tasted bad, as well as having the side effects of not being able to swim. If this this is the case, then her Devil Fruit cannot be a Smile, as Smile Fruits, unlike regular Devil Fruit’s, taste good.
Kaido also did mention that he went through a lot to get that Devil Fruit for her and that he didn’t intend on letting her have it. In theory, this could be referring to countless research and resources into the Smile Fruits but Kaido most likely means that her powers are rare. This means that just like Kaido, Yamato’s Devil Fruit is a Mythical Zoan-type.
Sadly, we will have to wait until One Piece manga chapter 1020 is officially released before we will have anymore information about her Devil Fruit. One Piece manga chapter 1020 is set to be release don the 31st of July, as One Piece takes a one-week break for Olympic Week.