Has anyone notice that some of the air slashes are either visible or invisible depending on whether or not busoshoku/ryou is present with their attacks or it can just be a different type of sword skill all together. For example with mihawk:
something tells me busoshoku emission was in play for the non-visible air slashes.
This might be an example of this as well with Zoro this time.
See no visible air slash is present but only the cut has been shown it's probably different in the anime but in the manga it probably shown this way to indicate busoshoku emission/ryou is being presented.
Invisible
visible





This might be an example of this as well with Zoro this time.

See no visible air slash is present but only the cut has been shown it's probably different in the anime but in the manga it probably shown this way to indicate busoshoku emission/ryou is being presented.