WARNING: The following contains spoilers for One Piece Chapter #1023, "Spitting Image," by Eiichiro Oda, Stephen Paul and Vanessa Satone, available in English via Manga Plus and Viz Media.
In Chapter #1023 of the One Piece manga, Kawamatsu and Hyogoro provide some interesting insight as to why Hiyori gave Zoro the sword Enma, which once belonged to her father Kozuki Oden. Zoro bears a striking resemblance to Shimotsuki Ushimaru. Not only does Zoro resemble the Daimyo of Ringo, but he uses the same sword style as him as well. Ushimaru, as we learn, was a descendant of Shimotsuki Ryuma, the God of the Blade. Kawamatsu draws the conclusion that destiny has brought Zoro to Wano, explaining that Ryuma was also a one-eyed samurai.
Once a great swordsman from Wano, Ryuma later became zombified after his corpse was stolen by Gecko Moria and reanimated by Brook's shadow. While he was an antagonist during One Piece's Thriller Bark arc, he also made an appearance in a one-shot called Monsters. In this one-shot, we see a younger Ryuma, and he's the spitting image of Zoro.
This isn't just a coincidence or a result of Oda's art style -- it raises the question of whether Zoro's homeland is Wano Country. We know he trained at a dojo in Shimotsuki Village as a child, named after Shimotsuki Kozaburo. It's possible that his parents are also of the Shimotsuki family and come from Wano. Everything about Zoro fits the aesthetic of the country, and he also shares the same blood type with Ryuma, which is XF. After what happened with Sanji, it's clear that blood type can give important information about a person.
It seems that fate has brought Zoro to Wano and that he will be instrumental in its liberation. Not only has he been given Enma, but he's also learned new techniques. He returned the sword Shusui, once Ryuma's weapon, to Wano. Everything seems to point to Zoro being a member of the Shimotsuki family in some way. Most likely, he's a descendant of Ushimaru and by extension, Ryuma. It's no accident that he brought Shusui to Wano and uses katanas in his fighting style.
How this will affect the story of One Piece is unclear, but Oda seems to be implying that it's extremely important for the country that Zoro has come. With so many people recognizing his resemblance to Ryuma, there's definitely something larger at play here.
