@Light:
1. She doesn't have a role for the crew.
1. At present, Yamato's ship role could be many things, including a role that seemingly appears inconsequential at this point to the journey of the Straw Hat Pirates. Until we get further focus on what exactly Yamato can do beyond fighting (and making Vivre Cards), certainty remains lacking.
When Yamato was introduced in chapter 984 I did wonder if Yamato could be a Stonemason and I have since entertained such a thought within a theory.
! @Syphin:
! > I still believe the role of Stonemason could come into play. If such a role served Gol D. Roger relevance when Oden performed it, Luffy (and Robin) may in turn also find a use for a Stonemason.
Oden's journal could have done more than inspire Yamato, it could have provided Yamato the knowledge required to become a Stonemason.
I have mentioned it before on the WG One Piece forums but I'll also include the post here (if you already read that post on the WG forums, this is just an edited version):
! Identifying a role for Yamato if they were to join the Straw Hat Pirate crew is a very curious task. Not only because barely anything has been revealed about a role required for the Straw Hat Pirates for the remainder of the journey but also because nothing concrete has been associated with Yamato in terms of what role they could perform. We also have to take into account the stage the story of One Piece is at because with the conclusion of One Piece in sight for Oda-sensei, they may not be much room left for adventuring reducing the need for traditional ship roles. Rather, if a character were to join the crew at this point in time, their main role within the crew would be story-driven. A secondary role performing task onboard the ship would arise as a byproduct from that story-driven role they primarily represent.
! With that said, what role could Yamato serve while journeying with the Straw Hat Pirates? To find that out, we can look at the character whom inspires Yamato the most, Kozuki Oden. The log keeper role Oden performed may or may not have relevance to Yamato, but I feel the logbook/journal was primarily introduced as a story-driving device opposed to setting up a new role a character could perform going forward. The journal was needed for Yamato to become who they are and will become the indirect reason for Wano Kuni’s liberation. Beyond recording his adventure in the journal and being a Daimyo, Oden actually performed other roles through his life. He was a powerful Samurai AND had attained the rank of Chief Stonemason when he worked in the quarry when he was a prisoner.
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! I had mentioned before in a previous post that the journal Oden kept may have the teachings of the Oden Nitoryu Style recorded within it. But what about the Stonemasonry skills the Kozuki Clan were renowed for? If Oden believed the Oden Nitoryu Style and the art of Stonemasonry reflected the culture of the Kozuki Clan, would he not have attempted to keep its existence alive by making a record of it for his son and future generations? This would have been even more imperative for Oden to consider when taking into account the state Wano Kuni was in before Oden resolved to challenge Kaido.
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! The journal Yamato possesses which they expressed contains “very important things” could be the avenue in which the restoration of the Kozuki culture can progress. And if the techniques of the Kozuki crafting/stonemasonry are recorded within Oden’s journal, it becomes necessary to establish a role for a stonemason/crafter within the One Piece world. But when you really think about the journey the Straw Hat Pirates have been on (since Alabasta), a role for a Stonemason aboard the Thousand Sunny may have already been established.
! What exactly does Robin believe her role to be? Way back during the Skypiea Arc, Robin mentions “I too have to guide the Poneglyph documents that I’ve read so far to the end of the Grand Line…to Laugh Tale.” In addition to performing that role, Robin is now also deciphering the Road Poneglyphs to lead the way to Laugh Tale.
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! But there is potentially something else of note that Robin mentions during the Skypiea Arc – “I’m sure that by connecting them and reading them they’ll become a document that fills in the “blank history” for the first time. Connecting them will complete a text, the real Poneglyph, which doesn’t yet exist. I’m certain that the Pirate King, Gol D. Roger, has delivered this document to its destination.“:
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! Notice a few compelling phrases that arouses intrigue? “First time”, “complete a text”, “REAL Poneglyph”, “doesn’t yet exist”. Curious statement, isn’t it?
! For those that believe Robin is the Straw Hat version of Oden are only half right per se. Sure, Robin can decipher the Poneglyph text but there is a key skill that Oden possessed which Robin currently does not…and that would be the ability to record the ancient language on the Poneglyph stone. Robin does not possess those abilities and as far as the story goes, that skill potentially died with Oden. Unless of course, Oden managed to record the Kozuki stonemasonry techniques within his journal which Yamato now possesses (and has for the past twenty years). Oden’s journal is the only place I can see any knowledge Oden wished to pass on to his son and future Samurai to be recorded. Nothing else has been highlighted at this point and Oden was never shown directly teaching anyone either his Oden Nitoryu Style or the Kozuki stonemasonry techniques. Oden had always expected to pass on such knowledge to his children.
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! In all likelihood, Oden used his journal to record those “important things” so that a record was left for Momonosuke/Hiyori and Wano Kuni after he was gone. Oden understood the importance of opening up Wano Kuni’s borders which is why he tasked his retainers with such a responsibility as his final wish. Likewise, Oden understood the value of keeping the Kozuki culture alive. This is why I believe, when Oden became aware that he may not survive the battle against Kaido, he used his journal to record the teachings of both the Oden Nitoryu and Kozuki stonemasonry techniques (and any other information he wanted to pass on). If Yamato did end up learning stonemasonry, their role could be intimately tied to that of Robin’s.
! Back to the statement regarding the text of the Poneglyph. It seems heavily directed toward a complete text of the Poneglyph being created for the FIRST time once all the information has been collected by Robin. But considering there is no one on the crew able to record such information on a certain indestructible stone, doesn’t that open a potential window for a certain someone who may have learned such skills from a certain journal that had contained “very important things”? Could Yamato be the person able to record the information Robin has accumulated over her journey onto a Poneglyph that “doesn’t yet exist”? As Robin had stated in the past, the “REAL Poneglyph”. Something to ponder on.
! But didn’t the Roger Pirates already learn the entire truth of the world such as the secrets of the void century, what the people of the D are, what the ancient weapons are, and Wano’s role in history? Yes, they did. So why is it necessary for Robin to collect that information again herself and for a record to be left, you ask? Well my friends, this is where Robin fans liberated by patience all around the world can take a deep breathe and let out a cry of profound ecstasy that shakes the mortal realm and echoes through the heavens. Robin may not be able to record the ancient language on a Poneglyph but what she can do is something ONLY she can do. That being, to understand the MEANING behind the words the ancient civilisation had left for the world. The Roger Pirates may have collected the relevant Poneglyph information/documents and learned the entire truth of the world, but did they truly understand what it meant?
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! Rayleigh cautions Robin about rushing to the end and advises her to take her time in her journey. One step at a time. Knowledge itself was meaningless without the ability to act on it. Rayleigh believed Robin’s journey with the Straw Hat Pirates could lead her, someone who studied alongside Clover and the Ohara scholars, to an answer that was different than the one the Roger Pirates arrived at. Through the conversation Rayleigh had with Robin, it certainly does appear the Rogers Pirates hadn’t fully grasped the will of the Ancient Civilisation. They had acquired the knowledge but not the meaning behind it and/or the means to act on what knowledge they had understood (ancient weapons).
! This is where Robin sets herself apart from ANY other character in One Piece. She is unique. She is the key to One Piece. She is integral in understanding the will of the Ancient Civilisation. She is without exaggeration, the most IMPORTANT character in the One Piece story. The Last Scholar of Ohara. The Hope of Truth. The Liberator of Deceit. The Agent of Change. The Light of Revolution.
! And for Robin to perform her role, I believe she requires someone with the ability to record her interpretation of the knowledge she acquired on a Poneglyph stone that will become the REAL Poneglyph. A complete text that does not yet exist. Such a record will be the force needed to cast the Tenryuubito and the World Government from their undeserved place as leaders and abusers of the World. With the inclusion of Momonosuke as a competing force against Im, a new world order will be created under the Wano Kuni faction that nations will begin to ally with against the World Government. Wano Dragon VS Celestial Dragon.
! In addition to reviving the Oden Nitoryu Style which Yamato will expose to the world as they travel with the Straw Hat Pirates, they will also revive the Kozuki clan’s stonemasonry teachings. After Yamato journeys with the Straw Hat Pirates to the end of the Grand Line, they will return back home to Wano Kuni and pass on that knowledge to Momonosuke and Hiyori (once the Oden Nitoryu Style and Kozuki Stonemasonry techniques are mastered during Yamato’s journey).
! Finally on a side note, with a Stonemason joining the crew, Luffy may end up finally getting the [Bronze] Statue he longed for:
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Considering how iconic statues have become in One Piece. Wouldn’t it be cool if Luffy was finally able to sate such a wish of attaining a statue of his own? Nami won’t be spending any money on acquiring one but if a stonemason were to join, that dream of getting a statue may manifest into reality. *Yamato crafts a statue of Ace on the Thousand Sunny. Luffy wakes up every morning crying at such a sight. Jinbe sighs every morning at having to console Luffy.
As for Yamato's story role, I have also put forward my thougths on that too.
! @Syphin:
! > We can already surmise what Yamato's dream is based on what has been revealed in the manga.
Oden had TWO wishes. One to open the borders of Wano and the second to assist the figure the world had been waiting for over the span of hundreds of years i.e. Luffy. It is pretty apparent at this point that Yamato has inherited the will of Oden and is currently fighting to see Wano Kuni liberated from Kaido and subsequently have the nations borders opened. Yamato has been in possession of Oden's journal for two decades but only came to realise the importance of the words contained in the pages after a certain event two years ago. Yes, prior to Ace's death, Yamato was not aware of the importance Luffy held in regards to the details of Oden's journal. This is why when Yamato first met Ace, he wished to leave aboard their ship because at that time he wished to be free and sail the seas going on adventures (which he still wishes for). If Wano wasn't chained by Kaido/Orochi and Yamato wasn't bound by the explosive cuffs, he would have got aboard Ace's ship. Fast forward ~2 years when Yamato learned about Ace's death, he also learned about Luffy and recalled what Ace told him years prior. Such memories about Luffy and Luffy's dreams connected to the writings in Oden's journal. Yamato realised at that time the person the world had been waiting on, the person Oden had been waiting for, was Monkey D. Luffy. This is the moment when Yamato knew what he had to do - what he wanted to do.
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Not only did Luffy, Zoro, Nami, Usopp, Sanji, Chopper, Robin, Franky, Brook, Jinbe and Sabo have their 'aha-' moment when Ace died but so did Yamato. Within the grief and sorrow, they found a path forward.
Ace's death allowed Yamato to make the connection between Luffy and Oden's journal (Yamato's "bible"). And this is why Yamato's dreams have evolved from what they were when he met Ace ~4 years ago (sailing the seas, going on adventures and opening Wano's borders) to what what he is expressing now on Onigashima during this arc. Yamato's dream is not only to help open Wano's borders but it is also to assist Luffy who is the person that will shake the world to its core creating waves of change. Yamato now understands how Luffy fits into Oden's SECOND wish and he is currently bearing that role on his shoulders.
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Yamato will join the crew and help them see through the unfulfilled work Joy Boy and Roger have left incomplete.
No other Straw Hat Pirate has been connected to Joy Boy and the mission they left behind. Not even Robin. She only learned about Joy Boy's existence a month ago in One Piece time and is still not aware of Joy Boy's relevance to the history of the world. Joy Boy was only revealed during the Fish-Man Island Arc AFTER the time skip. It is almost as if Oda had begun at that time setting the foundations for a new character (nakama) to fill a key story role aboard the Thousand Sunny that no current members at that time fulfilled. Yamato will assist in providing clarity to Robin about 'Joy Boy' and their place in history.
Alongside his admiration for Oden, Yamato is also expressing their own desires. Yamato will help Luffy liberate Wano Kuni and then the world. Fitting for someone who has been imprisoned and robbed of their freedom for the majority of their life.
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Yamato's interest in Joy Boy and the Dawn aren't inconsequential but rather a driving force behind his intentions and actions. Yamato is aware of Momonosuke and Luffy's importance to the future of the world and the "Dawn". Ever since Oden's hour long execution, Yamato has sought to be Oden. And after reading Oden's journal, he has wished to fulfill Oden's will. And within that wish he has combined his own desires - being free, sailing the seas and having adventures. Luffy is too important to Yamato and his dreams. The only way Yamato won't be sailing aboard the Thousand Sunny is if Luffy rejects him and that ain't happening. And Momonosuke won't be the one to rob Yamato of following their dream.
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Oden is a source strength for Yamato. While Yamato's need to imitate him may decrease going forward, the admiration and inspiration he feels and receives from Oden will remain. Oden's wishes will be fulfilled and Yamato will be the one to see it through via their adventure and journey to Laugh Tale (and beyond). Along the journey, Yamato will also learn more about their family origins and history. Kaido is a massive mystery and his story within Wano Kuni won't provide us with all the answers to the questions we have.
As for Yaamto's ship role, i wonder if Oda will just settle on Samurai for Yamato. He did want to be one and everyone else around the world views warriors from the nation as Samurai. Or does Oden constitute the highest level of Samurai to Yamato? I wonder if Samurai conflicts with Zoro's role. I'm still waiting to see if Yamato has stonemason skills O.o.
2. She hasn't had much interaction with the crew.
2. If there ever was a character who could join the Straw Hat Pirates with limited interactions with any of the Straw Hat Pirates outside of Luffy, it would be a character themed around Kozuki Oden, a character who joined the Roger Pirates with only interacting with Roger.
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Oda limiting Yamato's meaningful interactions to just Luffy is very intentional by him. As is also the Kozuki Oden theme he has based Yamato on.
Yamato spending limited time with the other Straw Hat Pirates may appear to be a negative but on the contrary it is actually more evidence toward Oda's intention in having Yamato become a Straw Hat Pirate.
3. Traveling to Laugh Tale might be counterproductive for her supposed future character development.
3. There exist a lot of story Yamato could be developed in through their journey alongside the Straw Hat Pirates, especially with it being confirmed that Kaido and Yamato have the blood of Oni/Ogres:
@Syphin:
Just as how Oden learned about the Kozuki history through his journey across the Grand Line with Whitebeard and Roger, Yamato will learn about the history of his blood (the race or races he belongs to) through the journey with the Straw Hat Pirates. Focusing just on Kaido (as Yamato's mother may yet become relevant), he isn’t just some human. He does not merely have horns. There is reason why Kaido is referred to as the Strongest Creature in the World. There is story behind his blood and the reason why he too is interested in Joy Boy. Kaido didn’t stumble upon Wano Kuni but specifically chose it. Oda has set-up the story of Yamato to extend beyond his admiration of Oden and the goals Oden held. The dream Yamato holds which Oda has reiterated several times across the arc is testament to the independence Yamato has to Oden’s story. Yamato will carry on Oden’s will and see it through but at the same time, he will follow his own desires and path before him.
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I have extrapolated on my interest in Kaido/Yamato's Oni blood which could enhance the relevance and development Yamato has in the upcoming Elbaf and Vegapunk story arcs:
! @Syphin:
! > Kaido: The Blood Of Oni
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Kaido/Yamato being confirmed to have the blood of Oni/Ogres is actually a huge development and one I have been waiting on confirmation for. And I still believe that the Ancient Giant tribe – which has not yet been named – are the Oni/Ogres Kaido mentions. Yes, the Ancient Giant tribe are Oni/Ogres.
Not only does Kaido bear a striking resemblance to the Ancients Giants we have seen so far in the manga who also resemble Oni/Ogres – Oars and Little Oars Jr (minus the size) – but he is also associated with Punk Hazard which is in turn linked to the story of Ancient Giants. Beyond the experiments conducted on the Numbers, Punk Hazard also contains other elements connecting it to the Ancient Giants; the larger-than-a-giant-skull with horns and the irregular warning symbol at the entrance of Punk Hazard. When this is taken together with the belief that Ancient Giants are Oni/Ogres, it makes complete sense why the Marines would take an immense interest in Kaido and the research into his Bloodline Element.
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Kaido’s Lineage Factor/Bloodline Element has become a substantial aspect to the research conducted by Vegapunk and the Marine Scientists. The CP-0 have already confirmed that when Kaido was captured by the Marines he was experimented on with his Bloodline Element being used by Vegapunk to create the Artificial Devil Fruit that Momonosuke has consumed. Beyond the Artificial Devil Fruit there are also connections with Kaido’s Bloodline Element being used to experiment on the Numbers. The connections they share with Kaido are too substantial to ignore as separate. Additionally, the Dragons Vegapunk developed also appear to be based on his research into Kaido’s Bloodline Element. Further, there may have been other subjects that were used in the research into Kaido’s Bloodline Element, specifically, the Jailer Beasts of Impel Down. The blood Kaido possess has become an incredibly valuable component in the Marines research in creating “weapons” that can strengthen their forces and I find myself curious as to how else the Marine Scientists (and Vegapunk) have weaponized Kaido’s Bloodline Element. Will Kaido’s blood and ancestry become a core story thread going forward as the secrets of the past hidden away by the World Government are uncovered?
The reasoning for why I believe Kaido’s Bloodline Element was used in the experimentation of the “Numbers” is because of the shared characteristics they have with Kaido and the interest Kaido took in them. The Numbers have displayed certain features and tendencies similar to Kaido (oni-features), mainly the horns and the love for alcohol. Kaido and the Numbers also share in the use of the same type of weapon – kanabō. Kaido could have realised the connection he had with the Numbers when they went up for sale on the black market and consequently purchased them as Big Mom mentioned.
In addition, the Dragons Vegapunk created to serve as guards of Punk Hazard (Dragon Number Thirteen and Small Dragon) are likely also based off his research into Kaido’s Bloodline Element. The naming convention of the Numbers and Dragon Number Thirteen suggest some connection regardless of the Dragon being named by a Tenryuubito. The reason the Dragons survived the Shinokuni poison from four years ago when Caesar activated his weapon and the battle between Sakazuki and Kuzan could be the result of having Kaido’s Bloodline Element. In addition to the thick skin, the flame breath could also have been the result of Kaido’s blood.
Turning to the Jailer Beast, what makes me believe they are related to Kaido? There isn’t anything definitive but rather an interpretation framed by reading between the lines. Something was clearly odd with the Jailer Beast when they were featured during the Impel Down Arc. Not only were their humans forms not revealed but their exact Devil Fruits were also kept a mystery not to mention the absence of speech. The Jailer Beasts may have been the initial attempts by the Marine Scientists at utilising Kaido’s Bloodline Element to enhance a soldier. Could Kaido’s blood have brought the Jailer Beast to a sort-of awakening Zoan state? Was this the original intent of the experiments on the Jailer Beast? The side-effects of such experiments could have rendered the Jailer Beast unable to shift back into human form and the loss of speech. The scene where Kaido viciously beats Yamato while he is on the ground in chapter 1025 reminded me of Minotaurus beating Jinbe while he was imprisoned in Impel Down. It could be a coincidence but when you also take into account the club and spike weaponry the Jailer Beast use and their “fish” lips (as a result of the Uo Uo no Mi?), one does wonder if there really is no connection between Kaido and the Jailer Beasts.
I believe the Marines took interest in Kaido beyond just his Mythical Zoan Dragon Devi Fruit. It was Kaido's blood that also interested them. The research they have conducted in Ancient Giants appears to be based around their research into Kaido's Bloodline Element and the data extracted. Such a possibility leads me believe that Oni/Ogres are Ancient Giants. And if this is the case, the relevance Yamato could have in the upcoming Elbaf and Vegapunk stories would be major.
Edit: Kaido's dialogue to Yamato (his disdain for humans) also implies that Yamato's mother was likely not human.
I have an old theory that Yamato's mother was the same race as King, so I wonder if that will pan out O.o.
There is also my recent theory on Yamato's relevance to Fish-Man Island and the story that could unravel there in the future:
! @Syphin:
! > The contemplation of possibility is indeed enthralling. I like speculation. Honestly, even if I disagree with a potential path, I don't deny the reflection of the imagery it wishes to paint. Whether it be for Bonney, Vivi, Tama, Hancock, Carrot, Caribou, Law, Crocodile, Yamato, a giant with the desire to explore and discover the potential of science, an alien looking for the history of their ancestors journey to a certain planet, a Tenryuubito attempting to change the world, a child of a MADS scientist seeking to follow in the footsteps of their parent or the mystery behind a certain bespectacled ice-themed yokai. I welcome all theories concerning all avenues, especially if it entails the far latter one, such would warm my heart. The existence of different angles not only inspires my perspective but allows me to view the story of One Piece in a much broader frame.
With that said, lets delve into the realm of possibility once again. This time, it deals with Yamato and their continued relevance as a Straw Hat nakama. At present, Luffy has no reason to destroy Fish-Man Island but I entertain that the precursor to such an act may very well be induced by the knowledge and context Yamato provides once sailing aboard the Thousand Sunny.
When the Straw Hat Pirates visit Fish-Man Island again, I suspect the Island’s deeper relevance to the Void Century will be covered as the story threads of Poseidon, the “Ship of Promise” Noah, Wano and Luffy are weaved together. Obviously when that time comes, the Straw Hat Pirates are going to need someone who is both aware of Joy Boy and familiar with the Mythical Zoan Dragon Devil Fruit. Thankfully, Oda has crafted a character that fills such a purpose in the Wano arc i.e. Yamato.
By nature of Joy Boy being intimately connected to Fish-Man Island, it can be extrapolated that at one point Fish-Man Island were close with the Ancient Civilisation and supportive of their intentions. The fact that Fish-Man Island housed several Poneglyphs including a Road Poneglyph before it was relocated (by Shanks?) speaks to level of connection between the two races and their role in the path toward the “Dawn”.
As mentioned above, the real and artificial Mythical Zoan Dragon Devil Fruits Kaido and Momonosuke respectively possess will hold relevance when the story of Fish-Man Island is brought into focus again. Considering the reverence attached to the imagery of a Dragon which the Ryugu Palace was themed around, it implies an affinity between the statue and the Devil Fruit form. Aside from the size, colour, mane and Kaido’s horns, the appearance of the Dragon forms between the three match completely. With such similitude, designs intentional by Oda, there certainly exist a connection between the Ryugu Palace Dragon statue and the Uo Uo no Mi, Model: Seiryu. And such a relation I believe WILL eventually be explored.
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As for the reason why Fish-Man Island attaches such veneration to the imagery of the Dragon, I suspect it may have to do with the role the Dragon played in their past. It may be possible that before Devil Fruit’s became a thing, Joy Boy possessed the ability to transform into a Dragon (a type of Fish that was able to swim in the ocean) which was eventually inherited by a Fruit – the first Devil Fruit? Or Joy Boy could have associated himself with the creature that is now represented by the theme of the Ryugu Palace. Joy Boy was likely able to converse with life forms (similar to Momonosuke/Oden/Roger/Luffy/Shirahoshi) and through such an ability bonded with the [Fish] Dragon. That connection may be what is being mirrored currently in Luffy and Momonosuke’s (Dragon form) battle against Kaido.
I also wouldn’t be surprised if by some twist of fate, the story also connects the Kozuki Clan with Fish-Man Island – the Kozuki stonemason being the ones to craft the [Fish] Dragon statue. The presence of Poneglyphs being on Fish-Man Island evidences the suspicion that the Kozuki Clan at one point was hosted by Fish-Man Island. Joy Boy may very well be a member of the Kozuki Clan. When the story is ready to delve into such details, having someone (Yamato) connected to the Mythical Zoan Dragon Devil Fruit (Kaido) and Wano will assist tremendously.
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Yamato isn’t just a character to serve as exposition but rather a character intentionally created by Oda to assist in moving the story of Joy Boy and the Ancient Civilisation forward when such a plot so far has been largely isolated from the Straw Hat Pirates adventure. With Oda’s sights set on the conclusion of One Piece, it is about time the Straw Hat Pirates align their path with that of Joy Boy’s and Yamato, as a nakama to Luffy, will assist in achieving such an end.
And lets not forget the potential of Yamato visiting Ace's grave - which he will get to by sailing aboard the Thousand Sunny.
@Syphin:
Yamato WILL meet Ace again and he will get to the memorial aboard the Thousand Sunny. So even if Yamato doesn't have their whole story explored within the Wano Kuni Arc, their relevance extends beyond this arc and into the story that will feature Luffy and the Straw Hat Pirates visiting Ace's memorial.
"The Sake I Brewed to Drink with You" - Yamato may not get to physically share a drink of sake with Ace again but he can share one with him in front of his grave on the Island near Sphinx.
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And lets also not forget that Oda has gone out of his way to write Yamato as part of the New Generation that will define the coming era. Wano Kuni is not the end of Yamato's story and focus.
4. She knows too much about the big mysteries.
4. Oden understood the importance of what was at stake and would not have included too much information in the journal.
@Syphin:
Considering Oden discovered the secrets of the world along with Roger, he would be aware of why the information the ancient civilisation knew wasn't openly shared and instead kept behind the text of the Poneglyphs that not anyone could read.
Just as Roger didn't reveal the secrets of world during his execution. Just as the rest of the Roger Pirates didn't reveal the secrets of the world. I don't believe Oden would have revealed the secrets of the world either verbally or through his journal.
Roger and Rayleigh knew the secrets of the world needed to be uncovered naturally through the journey. Oden would have felt the same which would have extended to what he wrote in his journal. Oden would have omitted the complete story of the Ancient Civilisation and only covered the brief details of his adventure and their discovery. The fact that Oden was resolved to opening the borders of Wano once he returned, he knew just like Roger what was at stake. I genuinely don't see Oden risking the Roger Pirates efforts by revealing all the secrets of the world in the journal.
Oden included just enough information in his journal to help guide the next generation (such as Momonosuke and Hiyori and those who would inherit Joy Boy/Roger's will) to completing what "Joy Boy" started.
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If Oden didn't share any of the information related to Laugh Tale and One Piece with Kin'emon it follows that he likely didn't include the information related to the "secrets of the world" within his journal. All that was included was information necessary to help support the figure the world has been waiting for i.e. Luffy (which is exactly the role Yamato will have a hand in serving).
Anyway, that's some of my thoughts on the "issues" surrounding Yamato.