One of the most relevant aspects to Yamato’s character is them being aware of Luffy for over three years since their encounter with Ace. Yamato has known about Luffy longer than any of the other Straw Hat Pirates. Back when they met Ace, Yamato wanted to join him on his ship but was overwhelmed by fear to make the leap. Ever since that moment, they have been waiting for Luffy, confident that he will arrive in Wano Kuni. Yamato has shown belief in Luffy for three years without even having directly met him. And along with using “Oden” as a source of strength to keep their fears at bay, they have also relied on the eventual meeting with Luffy as a “hope” to continue forward. Yamato believes Luffy will defeat Kaido and help open the borders of Wano Kuni.
Not only has Yamato been waiting for Luffy but as illustrated in chapter 996 they have been conscientiously following the Straw Hat Pirates journey. Yamato is aware of the Straw Hat Pirate members, their epithets and their bounties. Even their recent actions within Dressrosa, Yamato knows about it.
Normally that may not be so impressive but this is Wano Kuni we are talking about, a closed border country where very little information about the outside world enters. Yamato did not freely come across such information. They likely had to put in serious effort to acquire any newspapers or information brought in from the outside world by the Beast Pirates. Such commitment from Yamato regarding the Straw Hat Pirates expresses their interest, esteem and admiration for and in them. The extent to which Yamato is “involved” only adds to Yamato’s importance and potential chances in joining the Straw Hat Pirates because it reduces the amount of time needed for Yamato to familiarise themselves with the Straw Hat Pirates, their adventures and their objectives. Yamato can hit the ground running as a Straw Hat Pirate if need be (important at this stage of the story).
If it ends up being revealed that the Octopus who guided the Straw Hat Pirates to Wano Kuni was stationed there by Yamato because of their belief in the Straw Hat Pirates arrival, it would majorly help Yamato’s chances of joining the crew as it would establish that Yamato had a role from the very start of the Wano Kuni Arc. The Octopus seemed to be attracted aboard the ship after noticing the Straw Hat Skull Flag. And the Octopus only revealed itself and began to summon the Koi Fish after Luffy mentioned his name on the transponder snail (chapter 910).
Moving on to the crew dynamics, how would the interactions and relations between Yamato and the crew members look? Outside a few members that need a few assumptions to be made, a lot of the Straw Hat Pirate members would relatively easily gel with Yamato. Not much panel time would be needed to spend on fleshing out the relationship building.
- Yamato has met Ace in the past and cherishes such an encounter. Yamato forming a close bond with Luffy seems inevitable. Yamato can share stories of their time with Ace which Luffy WILL love. By extension, a bond between Yamato and Sabo will also exist;
- Yamato’s mission of mastering the Oden Nitoryu Style will see Yamato consult with Zoro, the future greatest swordsman in the world. Through such a relationship where a shared interest exist, a bond between the two will arise. Zoro would also not be against a female learning to master the sword (flashes back to Kuina), especially one as capable as Yamato;
- As for Nami, she’d love the information contained in Oden’s journal, especially if it detailed treasures existing on Islands (Islands not Laugh Tale). I can also see Oden’s journal being the foundation for the plot for a future One Piece movie where the crew journey to an Island mentioned in the journal containing a treasure;
- Yamato’s passion and romance for adventure will spontaneously allow for them to get close to Usopp and Chopper (and Luffy). In addition, if Yamato really is a stonemason, Usopp, Chopper and Luffy would totally love having works of stone created i.e. statues. And with Yamato being able to transform into a form potentially monstrous, I’m sure Chopper will find a kindred spirit in Yamato;
- From Sanji’s perspective: Yamato is a female. Side-boob. Sanji suffers 999,999 critical damage;
- Yamato being a stonemason will naturally allow them to form a close bond with Robin and allow for Robin to be featured more;
- Yamato has already met Franky whom has become interested in them. The enthusiasm Yamato has in Franky’s unique state will inevitable get them to form a close bond with him. While Yamato’s reaction to meeting General Franky may not have been complete excitement as is generally for male characters, they were still left in wonderment over his form and expressed their fascination at having never met anyone like him before in their life (someone whose met the strange and sad Beast Pirate SMILE users). Yamato establishes that female characters in One Piece can appreciate the spectacle that is General Franky;
- Brook. I don’t think there is anyone that wouldn’t be curious about a Perverted Gentleman Skeleton with an afro that has captured the world with his Soul King persona. Plus if Yamato did join, Brook will have another member in the crew with which he does not have to look down on due to his height (Jinbe and Yamato would be taller);
- Yamato joining could also help add relevance to Jinbe presence’s in the crew. Yamato has been “imprisoned” for twenty years and there is no way that such a reality and past would not create emotional and mental scars within them. Jinbe has experience with being among former prisoners (Tiger, Koala and other Sun Pirates) so if Oda wanted it explored, he could have Jinbe help Yamato with any trauma and mental anguish they may have – they will need help and Jinbe has helped Luffy through his mental trauma in the past. Robin after having met Koala (and being enslaved herself) may also have some insight in Yamato’s situation and be able to assist.
I believe the interactions Yamato will inevitably have with the Straw Hat Pirates throughout the Wano Kuni arc will indirectly craft bonds and a relationship between them and the Straw Hat Pirates.