Yamato is the son of Kaidou. Born as Kaidou's daughter and groomed from a young age to be his heir, Yamato instead developed a profound admiration for the legendary samurai Kozuki Oden. After Oden's death, Yamato decided to become like him, impersonating him and adopting his mannerisms. As a result of this desire to emulate Oden, Yamato decided to become a man and identify as Kaidou's son, with his father and the Beasts Pirates referring to him as such as well.