Warning: the following contains spoilers for One Piece: Ace’s Story, Vol 1, written by Sho Hamazaki and Stephen Paul, published by Viz Media
Ace is one of the most widely loved characters in the One Piece cast. As Luffy’s adopted elder brother, he has a huge role on Luffy’s growth as a pirate, but very littlewas known about his origins before the release of the light novel One Piece: Ace’s Story. This book establishes the origins of his first crew, the Spade Pirates. One member of said crew is a nameless man who goes by the moniker Masked Deuce.
Masked Deuce is a remarkably loyal man who follows Ace to the ends of the earth, chronicling their early adventures in the aforementioned light novels. So who exactly is Deuce? What is his motivation? What drives him to go on adventures with Ace and the rest of the pirates?
In Ace’s Story, Deuce in introduced as the nameless narrator, stranded on the same island as Ace. Deuce set out to seek adventure and glory on his own terms, much in the same way that Ace set out to be a pirate. While Deuce at first sees himself as far above criminal pirates, he soon realizes he misjudged both piratedom and Ace in particular, soon becoming a deeply loyal affiliate to him.
The two help each other get off the island together. Deuce almost takes Ace’s name out of respect for the pirate, only for Ace to convince him it would be more suitable for him to be named Deuce — a pun based on playing cards. From there, he becomes Masked Deuce, Ace’s right-hand man on the Spade Pirates. The two gather a crew and sail across the East Blue together. Later on, Deuce would travel with Ace to Wano. When Ace’s Spade Pirates were assimilated into the Whitebeard pirates, Deuce joined the medical staff.
The whole while, Deuce writes down the adventures to create a travelogue like the ones that inspired him growing up.
One of the most aspects of Deuce is his fierce loyalty to Ace. While he’s at first wary of Ace after learning Ace’s father is Gol D. Roger, the two end up sharing a Devil Fruit together (Ace inherits all the powers because he took the first bite) and helping one another escape from a deserted island. All of this helps establish Deuce’s fierce loyalty to the future pirate captain.
This loyalty leads Deuce to never doubt his captain for a second. Even when confronted with the marines and bounty hunters, at no point does Deuce ever doubt Ace’s incredible capabilities or powers. He proves his loyalty to the pirate captain time and time again. Even almost getting killed by bounty hunters doesn’t shake Deuce’s resolve.
Becoming Ace’s pirate eclipses all else in Deuce’s life. The mask he wears, in many ways, completely assumes whoever he was before meeting Ace. His old identity is eclipsed by Deuce. This begs the question if Deuce maybe is a little too loyal to Ace, either co-dependent or overly infatuated with him.
One Piece has introduced Ace's first mate: Masked Deuce. But we don't know who he really is because he gave up his name years ago.