In Chapter 1004 we see yet another woman wearing the paper eye mask. Maria says Sanji’s voice will be projected throughout the castle if he speaks while looking into the eye, so these masks can relay sound as well as visual signals.
The mystery here is only deepening – given that the symbol is also painted on Who’s Who’s chest, it would seem it is the eye painting itself that facilitates remote communication even if it isn’t painted on one of the paper masks.
This has to be the work of some sort of Devil Fruit and the individual responsible is still a complete mystery. There are separate divisions with Kaido’s crew – we know, for example, Sasaki was in charge of the Armored Corps, so perhaps Who’s Who runs the intelligence division of Kaido’s crew.
This still allows for a connection between Who’s Who and Cipher Pol and also explains why all of Kaido’s subordinates are also privy to the eye power. Basically, we know that Kaido’s crew area all using this power to communicate and also that it’s being used to share information with CP0.
What’s not clear is if Kaido, King, and Queen know CP0 is on Onigashima. They were likely invited by Orochi, who was dealing weapons. It’s possible, if Who’s Who is the intelligence officer in Kaido’s crew, he’s using that position to relay information to the World Government.
Who’s Who is the one who rooted out Drake as a member of SWORD and so this could again imply some sort of internal division between the Marine intelligence division (Sword) and the Celestial Dragon’s spies (CP0 – Shield).
Video Review: https://www.youtube.com/watch?v=Xgsg7dRPZbk
*Theory by StrawHatJedi