Shusui was not one of the twelve before becoming a Black Blade. Shusui was originally an ordinary blade that, when turned black by Ryuma, elevated it directly to the Meito class. The question is, what would happen if Ryuma took Whitebeard's bisento, which is already a Supreme Grade blade and among the top 12, and turned it into a Black Blade? Its classification would rise, potentially even surpassing Yoru.
Yoru's case is as follows:
- It was one of the twelve Supreme Grade blades before becoming a Black Blade, and upon turning black, it became the strongest blade in the world.
- It was a Meito that, upon becoming a Black Blade, became one of the twelve Supreme Grade blades (similar to Kozaburou's suggestion with Enma) and became the strongest.
If Shusui were a Meito before becoming a Black Blade, like Enma (upon becoming a Black Blade), it would be classified among the top 12. However, since Shusui is not one of the top 12, it is likely that it was not a Meito before becoming a Black Blade and only achieved that status after turning into a Black Blade.