Originally the Kozuki were not the rulers of Wano but were the stone masons and blacksmiths under the Ethan Baron family who are the actual rulers of Wano and Wano was one of the 20 kingdoms who fought against the Ancient kingdom
The fist Kozuki is the Kozuki Kitetsu who made both the first Kitestsu and Shisui. During that time the Shimotsuki were not Daimyos and Ryuma was a samurai who traveled the world, until he met Joy Boy and he is the link between him and the Kozuki’s in fact and after the events of the void century he was given the title of Daimyo
But he was the right hand of Joy Boy similar to JB, the events of Monsters was before he met Joy Boy and the beginning of the war and during the Void Century he killed the Ethan Baron God Knight and the first King of the 20. The one who pledged the empty throne oath later was his successor
The fist Kozuki is the Kozuki Kitetsu who made both the first Kitestsu and Shisui. During that time the Shimotsuki were not Daimyos and Ryuma was a samurai who traveled the world, until he met Joy Boy and he is the link between him and the Kozuki’s in fact and after the events of the void century he was given the title of Daimyo
But he was the right hand of Joy Boy similar to JB, the events of Monsters was before he met Joy Boy and the beginning of the war and during the Void Century he killed the Ethan Baron God Knight and the first King of the 20. The one who pledged the empty throne oath later was his successor