We know from the people Momonosuke has recruited to help fight Kaido that the story is based on Momotaro, the adventure of a young boy who recruits a Monkey, a Dog and a Bird to help him defeat 2 Ogres that look like a Tiger and an Ox.
We’ve already seen most of the parallels in the story with Momotaro (Momonosuke) recruiting the Monkey (Luffy), the Dog (Inuarashi) and the Bird is yet to come (Marco). But we’ve also seen the Ox (Kaido) so that only leaves the Tiger (Shogun).
So with each of them needing some kind of similarity with the creature from the Momotaro story, like Kaido with the horns, the Shogun should therefore have the appearance of a Tiger.
We all know that there was a traitor in the Minks, and this could be the Tiger Mink from Wano. It’s possible that the Shogun is a Mythical Zoan Tiger Devil Fruit user.
*Theory by misakghazaryan