Onigashima as an island is massive, especially given the scale of the ornaments Kaido used to decorate the ride to the main castle.
What I really wanted to get at was the massive skull that resides on the island itself.
It seems to have a very distinct appearance, that of the ancient giant race that Oars and Little Oars Jr. are descendants of.
This made me think that Kaido could be from the same race as Oars the Continent-Puller and Little Oars Jr.
As you see from these 3 images, the design of the horns of all these 3 characters is the exact same, so I’m sure Kaido is probably a half descendant of whatever race Oars and Little Oars Jr belonged to.
What do you think?
Theory by Starmie21