"According to Hitetsu, Enma will be classified as "Saijou O Wanamono" (Supreme Grade) if Zoro manage to turn it into Black Blade permanently."
AP.
Interesring and it confirms few things
- A sword can increase in rank by becoming a black blade
- Emma is a stronger sword than Shusui naturally, but currently it's in the same lvl as Shusui because it's not a black blade
- Oden didn't manage to turn Emma black, so Ryuma had better Ryu mastery had Oden
Though it makes me question what was Shusui's original grade? Was it even lower than now? What happens to a supreme sword if it gets turn black. Will it be of an even higher grade?