I, like many others, believe that Yamato will join the crew at the end of Wano. Those who don’t believe it think she just doesn’t have a place in the crew, and not without reason. The most common arguments are that: the only crewmembers she’s interacted with are Luffy and Franky, she tries too much to be like Oden which would make any interactions with the crew feel inauthentic, she knows too much about the One Piece (Oden’s logbook), and she doesn’t add anything to the crew besides fighting and sideboobs.

Thus, let’s address that last point that she wouldn’t add anything to the crew. Some have speculated that Yamato would join as the crew’s logbook writer, but Nami (and maybe Robin) already does this. Plus it’s not even that important of a role, and in my opinion, it would be incredibly boring if that’s all she did besides fight.

I believe the crew is still missing one more vital role/job (cook, doctor, musician, etc.). The crew is missing a brewer, someone to make alcohol. As far as I know, it’s never been explicitly stated how the crew acquires any alcohol. We know Franky needs to restock his cola supply for the ship, and he can’t make it himself so he (most likely) just buys as much as he can at each island they stop by.

I’m assuming this is the case with the alcohol supply as well. In real life, chefs at high end restaurants usually stick to making food and let the winery or brewery handle the drinks. Sanji is the greatest chef, but we’ve never seen him brew anything (he’s made mixed drinks for Robin and Nami, but never made alcohol from scratch), nor has anyone else on the crew (Zoro is a professional drinker and swordsman, not a brewer).

If the titles of chapter 999 (The Sake I Brew While Waiting For You) and 1000 (Strawhat Luffy) are meant to be Yamato’s words, then that’s an obvious hint that she knows a thing or two about making alcohol, so if she were to join the strawhats that would be her day-to-day job, while at the same time being a front-line combatant when the time comes.

As we know, Yamato knows mostly everything that’s written in Oden’s journal (the book was presumably scorched then soaked after Oden’s home was burned down, so some of the pages may not have survived). Some would rightfully argue that Oden wouldn’t have written blatant spoilers written in a book that anyone could easily just pick up and read.

But the Kozuki clan are known for their cryptic messaging, they’ve always hidden things in plain sight. Oden doesn’t have to spoil what the One Piece, he could just give hints. Or, if he knew nobody would suspect it, he could hide it in plain sight. We’ll get back to what Oden could’ve written later, but for now let’s bring our attention to the treasure itself.

If we assume that Artur’s Ultimate OP Theory is true, then that means the One Piece is Bink’s Sake. However, this theory makes the extra assumption that the One Piece is a recipe for Bink’s sake ( ビンクスの酒 ), and not the sake itself. The kanji for sake in Bink’s Sake is 酒 which is more of a catch all term referring to booze, rather than specifically Japanese sake. This means Bink’s sake could be a type of spiced rum or spiced wine, which I think would fit in well with the whole pirate theme.

I only bring this up to point out that Bink’s Sake doesn’t have to be plain old sake. It could still be sake, and in fact there is already a spiced alcoholic beverage called O-toso which is a spiced sake that is traditionally drunk on New Year’s in Japan. If Bink’s sake is actually O-toso, then that would tie in well to the One Piece bringing the often alluded to “Dawn of the World”.

So, I believe the One Piece, Bink’s Sake, is a spiced sake, O-toso, with some of the ingredients only being able to be found on Wano. In fact, the latest chapter (1040) may have been hinting at this when Big Mom suspected that “Some of it’s in this country too, isn’t it?”, referring to the One Piece in Wano.

If Yamato read Oden’s logbook and discovered what the One Piece is, and if the previous assumption about the One Piece being spiced sake is true, then logically Yamato would take up an interest in herbs and spices as she would know that this is important knowledge for whoever finds the One Piece.

Oden didn’t have to explicitly write what the One Piece is, he just had to write what was important or necessary for reaching the final goal. If that’s the case, then Yamato might not know too much about the series’ ending, which means any chance of her leaking spoilers to Luffy would be gone.

So if Yamato became interested in herbs and spices, then she would have studied Wano’s native plantlife as she explored the island growing up. We know Yamato isn’t a literal prisoner, she simply can’t leave Wano as the country itself is her prison. Thus, she had enough freedom to at least explore her interests (sake, herbs & spices) within the confines of Wano.

If that were the case, that Yamato is an expert in herbs & spices, then she might already get along well with some of the crew like Sanji (cooking w/ spice blends) and Chopper (spices or herbs with medicinal properties). But the one crew member that would like this aspect of her the most would be Luffy. That’s because Yamato may have developed her own spice/herb blends specifically for pairing with different types of meat.

I don’t think that she’d only apply her knowledge of herbs/spices strictly to beverages, as that’d be a waste. So with all that being said, people would still point to her lack of interactions as a reason she wouldn’t fit in.

But Robin hardly knew anyone besides Luffy when she forced her way in, and Luffy asked Brook to join as soon as he met him, before he even met the rest of the crew, and even before Luffy found out Brook is a musician. So I don’t think her lack of interactions should be used as a point against her joining, but for this next point let’s just assume it is.

The fans may not think Yamato fits in, but in the perspectives of the Captain and his wings, she fits perfectly. Back in Thriller Bark, after Luffy, Zoro, and Sanji got their shadows stolen and they were knocked out. Nothing would wake them up, not even Franky smacking the around. To them, the only thing worth getting up for was when Usopp yelled that “A beautiful lady swordsman just brought some meat!”

I know it’s a stretch with Zoro, being that Yamato uses a kanabo which means she’s straight up not a swordsman, but she’s a beautiful lady so Sanji is automatically opted in, and if all the above is true and she does know how to make good meat then Luffy would readily accept her too. Plus, I’m sure Zoro would appreciate having an in-house brewer, not to mention she’d be a great sparring partner since we know she’s always down to scuffle as seen with Ace.

However, some people still point to her whole “I’m Oden” schtick as a reason why she won’t join or doesn’t fit in, and to be honest I somewhat agree. I think that Luffy and Zoro (and maybe even Sanji) would take issue with this too. They may respect Oden’s story and struggles too much to allow someone to just pretend to be him while on the ship. But this would be easily solved by just making Yamato come to terms with her identity.

Once the arc is over, she no longer needs to be Oden, Wano has been liberated and opened up to the world, and Wano will have its new Shogun and defenders in Momonosuke and the Red Scabbards. There is no reason for her to pretend to be Oden. Maybe she’ll realize this and change, or maybe someone else will make her realize this? Idk, I’m not creative enough to guess how this interaction would go down.

And just as a preemptive counterargument, I know some people still believe Momo will continue to ride with the Strawhats whereas Yamato will be the one to stay behind to protect Wano. People point to Kaido’s statements about Yamato’s devil fruit to support this. But for now let’s just ignore the fact that Yamato has repeatedly stated she wants to join the Strawhats and travel the world, and let’s also ignore the fact that Momo has already stated he is the rightful Shogun of Wano.

Yamato, or rather Yamato’s devil fruit, is the guardian deity of Wano, which people take to mean she must stay. But what exactly is it supposed to be protecting? People interpret this as being a literal protector of the village/country, presumably from outside invaders. However, according to this, the Makami was a guardian deity who would protect crops from boars and deer. So not necessarily a protector of the country itself, but a protector of the country’s goods.

If all the above is true then Yamato was not Wano’s guardian, but the guardian of Wano’s one-of-a-kind native plant-life. Perhaps the plants she needs to protect are the ones needed for Bink’s Sake? We know that Orochi has decimated the land by polluting everything, so obviously Yamato has failed in that regard. But it’s still possible that somewhere on the island Yamato has a hidden nursery/greenhouse/farm to preserve what little plant-life there is left.

Theory by Titonutz (https://www.reddit.com/user/Titonutz)