Since the original penning of this article, the manga has provided us with a definite answer. Yamato is a trans man and uses “he/him” pronouns.
After his death, Yamato chose to become Oden, impersonating him and adopting his mannerisms. As a result of this desire to become Oden, Yamato decided to become a man and identify as Kaidou's son, and Kaidou and his crew refer to him as such as well.
The introduction box on that page refers to Yamato as “Kaidou's daughter” even though she has only been called Kaidou's son in the story. Additionally, the Vivre Card - One Piece Visual Dictionary lists Yamato's gender as a female in her card entry and then even goes on to refer to Yamato only using she/her pronouns.
Yamato may be known as "Kaido's Son" but is biologically a girl. However, what has attracted so much attention from the community is the respectful and casual approach the series has taken with this story. Yamato was so inspired to be like Kozuki Oden that he sought too, to identify as a man.
Yamato Takeru's Wife Tachibana-hime Calms the Storm by Jumping into the Sea at Kazusa Bay.
Isuka is a brave woman with a strong sense of justice, as she was willing to confront the Spade Pirates alone on their ship in order to arrest Portgas D.
Takeo Gouda
Takeo's Yamato's boyfriend. In the first episode, when she was heading back home from school, Takeo rescued Yamato from being groped by a pervert.
Yamato is the daughter of Kaido. She is otherwise widely referred to as his son due to often presenting herself as a man as a result of her profound admiration for the legendary samurai Kozuki Oden and her aspiration to emulate him.
Yamato being a few years younger is more apparent back when they were in ANBU, when it's easy to see that Kakashi is further along puberty and taller than Yamato is. At the end of Shippuden, Kakashi is 31 and Yamato is 27.
In fact, Yamato openly declared that he would join Luffy on several occasions, however, in the end, he changed his mind. Yamato decided to stay back in Wano simply because Oden started his journey by going from region to region in Wano as well. Yamato still idolizes Oden and wants to follow in his footsteps.
4) Yamato is biologically female
Yamato doesn't have a traditional male body, that much is true. Regardless, he still identifies himself as a man, because that is what he corresponds with. Yamato wants to be male because Kozuki Oden was male.
Yamato needs Luffy's approval to join the crew and, once he gets it, he's officially going to be the 11th member of the Straw Hat Pirates.
Yamato Takeru, in full Yamato Takeru No Mikoto (Japanese: “Prince Brave of Yamato”), Japanese folk hero, noted for his courage and ingenuity, who may have lived in the 2nd century ad. His tomb at Ise is known as the Mausoleum of the White Plover.
Yamato is Oden's daughter and has been referred to as such; however, on numerous occasions, Yamato has been called "Kaido's son." Even Kaido openly calls Yamato his son, causing confusion over the character's gender identity.
Kaido literally called Yamato his son twice. Yamato said he became a man. The entirety of Beasts Pirates refers to him as a man. It's not that hard to respect pronouns.
The dragon, who assisted to the whole thing, immediately fell in love with her and asked her to marry him. The woman, who was perfectly aware of the dragon's evil actions, was none other than the goddess Benzaiten herself.
Many One Piece fans love the way Yamato looks. The Oni Princess is far taller than regular humans. With her giant club and red horns, she invokes the appearance of Japanese folklore demons. She embodies the very concept of power, just like her father.
Kaidou at age 39. Kaidou's outfit during the Timeskip. Kaidou's outfit during the Zou Arc.
Mei is Yamato's current love interest, his girlfriend, the special someone who he cares and loves, and they two are currently dating.
Jong-hak Baek: Nami's Husband.
At Jump Festa 2002, Inaba was cosplaying as Nami for a One Piece stage show. It was there that she ran Eiichiro Oda, and the two hit it off. They dated for a couple of years and married in 2004.
Ship Tease - In occasional chapter covers, in the manga, anime and film, Luffy and Nami are given moments that can be considered 'romantic', with some people having commented on romance between the two (Sanji) or compared them to a romantic couple (Tesoro).
Yamato is the daughter of the Strongest Creature in the world, Kaido, and an unnamed woman, however, the current status of her mother is unknown. She is presumably a child of an Oni, indicative from her horns.
The most well-regarded theory is that present-day Yamato Japanese are descendants from both the Yayoi people and the various local Jōmon people. Japanese people belong to the East Asian lineages D-M55 and O-M175, with a minority belonging to C-M217 and N-M231.
They seem to be part of their bodies, in which case Yamato most likely inherited their horns from Kaidō. The two may be a new race of humans that hasn't yet been fully elaborated upon. In any case, it's clear Yamato's horns are something they were born with.