So to turn a sword black you need :
-That the sword have done a certain amount of fight (amount being unknown)
-A certain level of haki from the swordsman (level unknown)
-CoC
-Sword will?
-The sword being old enough
The wado ichimonji was create by Kozaburo too but was never in as many fights as Enma therefore by this logic Zoro will not be able to turn it black, I guess
-That the sword have done a certain amount of fight (amount being unknown)
-A certain level of haki from the swordsman (level unknown)
-CoC
-Sword will?
-The sword being old enough
The wado ichimonji was create by Kozaburo too but was never in as many fights as Enma therefore by this logic Zoro will not be able to turn it black, I guess
Wado might be the last one to turn black if the previous battle is not use it many time with haki. But i think enma going tp be the first one since it oden's