WARNING: The following contains spoilers for the future events of the One Piece anime, written by Oda Eiichiro and available for streaming now on Crunchyroll
The sudden revelation that Kaido has a child is still one of the biggest twists of the Wano Kuni Arc so far, making Yamato a mysterious figure in deep need of full character exploration. While very little of Yamato's backstory has been given away (aside from a few brief flashbacks,) the reveal in chapter 1020 that Yamato consumed the mythical "Inu Inu no Mi, Model: Oguchi-no-Makami" devil fruit offers unique insights into what influenced Oda's construction of the character.
Researching the history of the Oguchi-no-Makami deity in Japan exposes clear connections between the character and the legendary figure of Yamato Takeru no Mikoto, potentially offering a glimpse into what Oda's intentions are with the character and what the future may hold for Yamato.
The White Wolf and the Mountain God
This small act guided the two recipients down the correct path and instilled new belief in the frightened Momonosuke. This itself, may also be an allusion to the origins of wolf worship in 2nd century Japan, whereby a white wolf appeared before Prince Yamato Takeru and guided him safely through the demon-infested woods of a mountain. The prince would later have a shrine built atop Mount Mitsumine, to respect the wolf deity that aided him and the mountain wolves in general, who were seen to protect houses from fire. Similarly, Kaido explains in chapter 1020 that the Makami is revered as the "guardian deity of Wano", and in the most recent chapters, Yamato is rushing to prevent fires within the skull dome from reaching the armory.
The Legendary Prince Yamato Takeru
Another noteworthy legend of Yamato Takeru that Oda adapted into his story involves one of the dangerous expeditions the prince was sent on, which saw him tasked with killing the last surviving leader of the Kumaso, "Torishi-Kaya". In order to achieve this feat, Prince Yamato disguised himself, cross-dressing as a maid in order to infiltrate the leader's banquet and assassinate him. Oda took inspiration from this and added the cross-dressing element to Yamato's character as a facet of her adoration for Kozuki Oden.
Another minor comparison that can be drawn involves the character's physical stature, with Emperor Keiko being recorded at ten feet two inches in height. His exceptional size would easily place him within the realm of gigantism in modern society, a trait which he seemingly passed onto his family and which is mirrored in Kaido dwarfing most One Piece characters at 23 feet three inches tall. Yamato also stands taller than most of our main cast at eight feet eight inches tall.
What Can History Tell Us Of The Future
Although there are a lot of calls for Yamato to join the Straw Hat Pirates after the conclusion of the Wano Kuni arc, looking further into the legends of Yamato Takeru suggests a much darker potential outcome. The end of Yamato Takeru's story came after he blasphemed against the God "Ibuki Daimyōjin" and was subsequently cursed by the deity, leading to the Prince falling ill and dying shortly after. The Ibuki Daimyōjin is described as a white boar equal in size to an ox and has already been referenced by Oda with the Mountain God incident of Oden's flashback.
However, in the context of the current story, Kaido is representative of a God like power within Wano (matched only by the presence of Big Mom,) which may imply that Yamato will fall at the hands of one of the Four Emperors currently present by the end of the war. Delving one step deeper, Oda may choose to adapt the curse which killed Yamato Takeru using Big Mom's "Soul Pocus" ability, having the Emperor steal the majority of Yamato's lifespan from her.
Alternatively, the legends also state that Yamato Takeru was once gifted the "Kusanagi no Tsurugi", a legendary sword found by Susanoo within the body of the defeated Yamato-no-Orochi. This leaves the possibility of Yamato playing some key role in the final moments of Kurozumi Orochi, or at least gaining some new form of weapon as an upgrade for if she were to join the Straw Hats on the final part of their voyage. Receiving a sword like the Kusanagi no Tsurugi, to either wield alongside or in place of her Kanabō, would also further Yamato's ambitions of being like Kozuki Oden and open up the possibility for her to learn the Oden style nitoryu.
As the story continues and Wano reaches its ultimate conclusion, the extent to which Oda has chosen to continue adapting the life of Yamato Takeru into One Piece will come to light, but given the number of subtle and direct references within the Wano Kuni arc so far it is highly likely he will want to conclude the history (even if he switches the death onto a character besides Yamato to please the fans.)