"Zihuan, right?" He's not exactly sure what a style name is or what the significance is, though he does immediately connect it to Law's own full name - though as far as he knows, the guy doesn't use "Water" with anyone at all, and the D in his name is another thing entirely, so it's not an exact parallel. Mostly, he knows Cao Pi sometimes introduces himself as such in formal communications, so he had taken it for something formal. Guess that wasn't entirely right.