The former first mate of the Whitebeard Pirates and the de facto leader of its remnants, Marco “the Phoenix” is a crucial character in One Piece. The formerly neutral vice-captain allying with Luffy during the Wano arc represents a great deal for both the Straw Hats and the world stage as the two major powers come together.
This is why it’s odd that Marco really hasn’t done much so far. His role in the Wano arc was teased as far back as Chapter 820 where the Straw Hats discuss recruiting him, and then in Chapter 909 where he seemingly refuses Cat Viper's call to action. As such, it’s a shock when he shows up in Wano after all, ready to fight with the alliance against Kaido.
All Marco has done so far, however, is briefly distract King and Queen. Fighting two Yonko Commanders at once is certainly no small feat, but the series doesn't pretend their fight is important -- Marco himself makes it clear that he’s just holding them off for Zoro and Sanji to deal with. With Zoro and Sanji now fighting the two Calamities, Marco seems to have bowed out entirely, and somewhat anticlimactically given how much buildup he had. As the sole guardian of Whitebeard’s hometown, Marco made it clear that he would only leave in the most extreme circumstances, and his role so far hasn’t justified that decision.
It’s entirely possible, however, that there's something else in store for the Phoenix. The Wano arc is a partial retelling of the Tale of Momotaro, a Japanese folktale about a boy named Momotaro who, with the promise of millet dumplings, persuades a trio of allies to fight a demon that lives on an island called Onigashima. In One Piece's loose adaptation, Kozuki Momonosuke is named after Momotaro, and Kaido’s headquarters, Onigashima, is the same as the demon's island. The character Tama also uses enchanted millet dumplings to win Kaido’s forces over to the alliance’s side.
One key detail from the tale is the identity of Momotaro’s three allies: a monkey, a dog and a pheasant. Momonosuke, meanwhile, has allied himself with Monkey D. Luffy and Yamato, wielder of the Okuchi-no-Makami Devil Fruit -- a wolf deity. This means that the folktale’s monkey and dog have direct parallels in One Piece, but the pheasant is still unaccounted for. Given Marco's phoenix Devil Fruit powers, he's the only major hero with a bird motif currently on Onigashima, making him the most feasible candidate.
While Marco's reduced role thus far might make him a confusing choice for the pheasant, it would be a deceptively apt choice. After all, the concept of inherited will is one of One Piece's main themes -- Marco is the main inheritor of Whitebeard's will, and Momonosuke is the inheritor of his father Oden's, himself a former Whitebeard Pirate. The Wano arc is Momonosuke's coming-of-age story, and it would be fitting for him, as Oden's proxy, to stand alongside Whitebeard's.
That's all very well for Momonosuke's character arc, but Marco's won't be so clean cut. The former Whitebeard Pirates first mate has had a hard time of things. Following the events of Marineford and the subsequent Payback War with Blackbeard, Marco's stint as captain of the Whitebeard Pirates hasn't been particularly successful. The man lost his adoptive father and brother on the same day, and his crew is currently scattered, leading to Marco becoming a recluse -- but fighting alongside a Kozuki again is just the boost the Phoenix needs. It’s Momo’s goal to open Wano's borders and accept responsibility on the world stage, and Marco doing the same would parallel that plotline beautifully. After all, matching its world’s broad political gestures with more intimate character beats is One Piece’s bread and butter.
Plus, as the inheritor of Whitebeard’s will, Marco will come to the forefront of the story sooner or later. Oda has confirmed that the self-proclaimed son of Whitebeard, Edward Weevil, will play a big role in the series moving forward, and he has his eyes set on slaughtering the remnants of the Whitebeard Pirates. If Marco is going to be part of the inevitable confrontation with Weevil, then he’s going to need to get his groove back first, and the climax of Wano is the perfect opportunity for him to do so.
Marco, at present, is an outlier in this arc. For all of the intricate plotting, his role in the story is still a mystery. But Oda is a deliberate writer, and Marco’s seeming lack of presence thus far and the absence of the pheasant is no coincidence. Whatever the climax of the arc looks like, and whatever course Marco’s character takes, it's a sure thing that no one will see it seen coming.
