Yamato greatly admires the legendary samurai Kozuki Oden to the point of even proclaiming to carry his identity. She has referred to herself as Oden on multiple occasions and has even emulated his gender, referring to herself as the “son of Kaidou” due to Oden being a man.
Although initially carrying doubts as to how to present as Oden, Yamato has steadily expressed a straightforward attitude regarding this identity as time has gone on, even proclaiming herself as such to Oden’s son Momonosuke, to the boy’s horror.
In a recent Vivre Card packs, extensive information regarding Yamato’s gender identity has been provided.
In her sex/gender section on the card, Yamato is referred to as “female” with no extra connotations. In the back of the card, she is more than once referred to with female third person pronouns when described. And, in her description, she is referred to as “the Princess of the Beasts Pirates” and “the Oni Princess“.
The Vivre Card makes it very clear that it wants to address Yamato as female. Mentions of Yamato becoming Oden are made, but still done with female pronouns.