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What does Kaido have to do with the 20 kingdoms that fought the Ancient Kingdom 800 years ago?
I don't know if you're prepared to read what I'm about to say but Kaidou was sent to the future, he is actually the cause of all revolution, the trigger of war, middle and end of it.
He'd come to the fore to make sure the government didn't get their hands on Wano and had done so this entire time, he and Ryuma.