Onigashima as an island is massive, especially given the scale of the ornaments Kaido used to decorate the ride to the main castle.
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What I really wanted to get at was the massive skull that resides on the island itself.
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It seems to have a very distinct appearance, that of the ancient giant race that Oars and Little Oars Jr. are descendants of.
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This made me think that Kaido could be from the same race as Oars the Continent-Puller and Little Oars Jr.
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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