One Piece, one of the longest-running manga and anime series and the shonen genre's all-time greats, is set to end within five years. With many story arcs needing to be wrapped up and final battles needing to be fought, it's easy to forget about Gol D. Roger and his mysterious treasure. From the very beginning, finding Roger's fabled "One Piece" has been the driving force pushing the entire series forward, motivating countless characters to act when necessary and fight when possible.
But this begs the question: what is One Piece? What is the mysterious treasure that Roger left behind? The announcement of its existence started the Golden Age of Pirates, urging thousands of pirates to search for the mystery prize without knowing what it is. With this in mind, let's run down some and weigh up some of the best theories.
FRIENDSHIP IS THE REAL REWARD
Many people believe that the treasure will turn out to be absolutely nothing. Roger, upon being executed, deliberately made up the story of One Piece and his treasure in order to spur on more piracy. Should someone find it, they'll already become the greatest pirate in the world, which is a prize in and of itself. What if the real One Piece was simply the journey itself and the friends Luffy -- or someone else -- made along the way?
We can rule this one out easily. Mangaka Eiichiro Oda confirmed that Roger's treasure is a physical reward. Furthermore, when Marshall D. Teach killed Whitebeard, Gol D. Roger's rival and confidant, the old pirate confirmed that the world would be "shaken to its core" when One Piece is found. So whatever this item is, it will prove to be something real and profound.
A PERSONAL TREASURE
One recurring motif in One Piece is the idea that treasure isn't always gold. Luffy's hat is a treasure to him, but it isn't worth anything -- It's just full of sentimental memories. Likewise, perhaps Gol D. Roger's treasure isn't a massive amount of gold, but perhaps some personal item of his.
This is further emphasized by the viewpoint many of Roger's pirates had that personal treasure holds more value than monetary treasure. Something meaningful to Roger would be far more than a gold chest.
Given this, One Piece could ultimately be some useless trinket. Though, this wouldn't match what Whitebeard said, unless the way the world would be shaken to its core is in regards to how disappointing Roger's treasure is to gold-seeking pirates.
A MISSING PIECE OF HISTORY
Another promising theory is that One Piece will be a Poneglyph. Poneglyphs are huge tablets written in an ancient language, detailing the history of an ancient people. There are 30 in total. Nico Robin, one of Luffy's crewmates, can read them, but she seems alone in this skill. The Word Government has declared them dangerous weapons, partly because of some detail the existence of three superweapons: Poseidon, Uranus and Pluton. They are indestructible.
Poneglyphs were first made in Wano Country by the Kozuki Family, used to detail the events of the Void Century. Gol D. Roger is a descendant of this family.
There is a lot of evidence that One Piece is tied to the Poneglyphs in some way. Four "Road Poneglyphs" that instruct people to follow a certain path leading to Raftel, an island that only Rogers and his crew ever reached. Many believe One Piece is hidden on this elusive island.
Further adding intrigue, during the Skypedia Arc, the Straw Hats found that Gol D. Roger left his own message in the language of the ancient people, telling anyone who read it to, "Keep moving forward."
It is possible One Piece is simply a Poneglyph detailing some unknown fact of history -- something that would be earth-shaking knowledge -- or it is a Poneglyph of Roger's own creation.
PLUTON, URANUS AND POSEIDON
The three superweapons outlined by the Poneglyphs have been referenced throughout the series. Poseidon is a special ability available to Mermen to control all sea life, even the all-powerful Sea Kings. Poseidon is currently possessed by the Mermaid Princess, Shirahoshi. The other two, however, remain shrouded in mystery.
Pluton is a huge battleship capable of demolishing whole islands. Franky, Luffy's resident cyborg, had a blueprint of the ship that he ultimately burned. Even less is known about Uranus, which is said to simply be an all-powerful weapon that can destroy the world in the wrong hands.
It is said that Gol D. Roger found the three weapons, though this is unconfirmed. It is known, however, that Roger never used the weapons. Because to their ties with the Polygraphs, it would appear that One Piece could be either the Pluton or Uranus -- or, perhaps, both of them assembled literally into one piece.
JUST A BIG OL' PILE OF GOLD
The most disappointing end destination for One Piece would be learning that Roger's treasure is just a lot of gold. It would lack any thematic resonance and be, in many respects, immaterial. After all, there are tons of gold supplies throughout the Grand Line. Tons of characters are insanely wealthy.
Besides, what would Luffy do with all that gold? What would Luffy, a person who values a straw hat and adventure over riches, do with all that money? One Piece should symbolically represent Luffy's goals -- or, at the very least, something Roger valued.
Alternatively, One Piece can be something of monetary value, like the deed to a certain landmass. Property that can be sold off, or, perhaps, something can alter the economy of the world government. Perhaps it is some secret that could tie disparate things together to create more harmony. Or, perhaps it is a piece of wisdom that can offer a chance to make more riches.
While this speculation is ultimately futile until Oda gives us our answer in five years time, fans should remain optimistic that Gol D. Roger's secret treasure will not be something as superficial or obvious as a whole lot of gold, or something as abstract as a mere sense of accomplishment.