This is a simple explanation: Zoro respects Honor heavily, especially when it comes to swords. He would respect the graves of Wano.
We know from multiple characters, especially Onimaru/Gyukimaru, that grave robbing in Wano is a serious crime, especially over Samurai.
I believe that Ryuma, who is worshipped as a God in Wano, the God of the Blade, would have a very special Grave; a Grave only Royalty of the country can access.
Zoro most likely asked Kinemon/Hiyori/Momonosuke to visit the grave, but was then told that the Grave is a Sacred Site.
I doubt even Kinemon/Scabbards would be allowed there.
Zoro will visit Ryuma's Grave when we return to Wano, after Teach attacks for Pluton, and Momo requests aid from the Straw Hat Pirates. They couldn't beat Green Bull; they can't stop Teach.
We know from multiple characters, especially Onimaru/Gyukimaru, that grave robbing in Wano is a serious crime, especially over Samurai.
I believe that Ryuma, who is worshipped as a God in Wano, the God of the Blade, would have a very special Grave; a Grave only Royalty of the country can access.
Zoro most likely asked Kinemon/Hiyori/Momonosuke to visit the grave, but was then told that the Grave is a Sacred Site.
I doubt even Kinemon/Scabbards would be allowed there.
Zoro will visit Ryuma's Grave when we return to Wano, after Teach attacks for Pluton, and Momo requests aid from the Straw Hat Pirates. They couldn't beat Green Bull; they can't stop Teach.