Its pretty much confirmed that Koshiro the father of kuina is from Wano. Oda said in a recent sbs that some people left wano and entered east blue, but did not want to spoil anything. And in this chapter 939 we see that people from Wano call haki differently, and hyogoro gives us a description. That its an ability which allows swordsmaster to cut through anything or nothing. The ability to cut Through toughest steel or to not cut even the trim paper. This is a direct Quote from Zoro`s swordmaster/sensei Koshiro.
Now this open questions:
"Why and How did People leave Wano a country which borders arent open?
"When did they leave the Country?"
I think They would not leave the country easily or for no reason. It simple must happened a major even which led to emigration of wano. I think the only Major event befitting that would be the death of Oden when Kaido and Orochi took over the country 20 years ago.
And i think that the shadow figure from Denjiro, who has a ponytail looks exactly like Koshiro, who also has a pony tail.
Now people might they that the shadow figure does not look identical with Koshiro but i think this was intentional to no spoil us and since when were shadow figure identical. And Oda can simple excuse this by saying it was 20 years ago.
Plus thee second act of Wano is almost over and there wasnt a guy introduced with a pony tail yet which would also support this idea.
Zoro take his place of "The Nine red Scabbards". This would be an interesting plot line for Zoro, someone who fills the space left open by his sensei.