I want to talk about Who’s Who. When he faced Jinbe in the latest chapter, he said that he knew and seen him before.
My crazy idea is that Who’s Who’s is Masked Deuce.
Ace’s best friend and his first crewmate. Deuce has no name and no identity. He even introduces himself to Ace as “the one with no name” and then says he’ll be the deuce to Ace, taking the name of Masked Deuce on his travels with him. You can see more of this in Ace’s Story chapter 1 drawn by Boichi. He also sports a mask to emphasize this lack of identity theme. Who’s Who mentions that he knows Jinbe from when he was a warlord and Jinbe asks him to take off his mask, which he refuses.
We know that Deuce was with Ace when he fought Jinbe while still a captain of the Spade Pirates, and then he and the rest of them joined Whitebeard. Besides this, we don’t know what’s become of Deuce and he hasn’t been shown in the story yet. I doubt someone as important as Ace’s best friend and first nakama would just be forgotten.
Think about it, both of them meet these criteria:
A hidden identity;
A mask to cover their face;
A similiar cryptic name (Masked Deuce, Who’s Who);
And finally, their colour schemes are polar opposites: Deuce is blue-coded, while Who’s Who is red-coded.
Last but not least, this might be a stretch, but Deuce was fascinated by stories of giants and Ace charmed him by telling him the story of the continent-puller, which many hints indicate we’ll learn more about in this arc, such as how the skull in Onigashima could belong to that legendary giant. It’d only make sense for Who’s Who to be there then.
How did it lead to this though? Considering their friendship, it’s possible that sometime during the timeskip Deuce left the Whitebeard Pirates following Ace’s death. He eventually started his own crew until he and Kaido met and his will was broken, becoming a servant of him. And he dyed his hair pink I guess. Considering how Ace is becoming more and more relevant in Wano, I think it’s very possible we’re leading up to such a reveal some time in the future.
*Theory by Chris Mic