Board Thread:Versus Debates/@comment-28635066-20160603012021/@comment-734582-20160605202153

I believe Sage Transformation (Juugo style) is actually what Snake Sage Mode is. That is, the ancient white snake (or whatever the name) bites you similar to Orochimaru.

Since Curse marks were controllable, clearly Sage Transformation is. And it seems Mitsuki achieved a perfect Sage Transform.