Yamato is the daughter of Kaido of the Four Emperors and self-proclaims to be "Kozuki Oden". This profound admiration for the legendary samurai has led to the decision to embody everything related to the samurai to the extent of proclaiming to be a man as well, and hence Yamato is widely referred to as Kaido's son. Yamato is tall, being slightly over twice Luffy's height but not nearly as tall as Kaido. Yamato has long, white hair that is bound between orange rods into a ponytail at the back, which fades into aqua green and then blue the further down it goes, and ends in rectangular locks similar to Kaido. Yamato also has large, orange eyes with prominent eyelashes, and wears gold hoop earrings on both ears and has red horns. Clothing-wise, Yamato wears a pair of red hakama pants and sandals, and, much like Oden, wears a large purple and white nio-daisuki behind the back. Yamato's current outfit is a sleeveless white garment with a diamond-shaped design on both sides and an indigo, wisp-patterned bottom half. This garment was originally a sleeved kimono with long white sleeves, but these were later ripped off, leaving the garment sleeveless and making it more form-fitting. Also, while in disguise, Yamato originally also wore a hannya mask, which has a wig with an extremely long and wild mane attached to the top and a long goatee attached to the bottom. Around 3–4 years ago, Yamato wore a long-sleeved outfit similar to her current one, but with different symbols on the breast area. The symbols resemble an oden skewer.
Yamato holds immense admiration for the legendary samurai Kozuki Oden, emulating every aspect of him, including his name, appearance, goals, and even his gender, reasoning that, since Oden was a man, then it was also necessary to become a man. Yamato wishes to fulfill Oden's dream of reopening the borders of Wano Country. Due to this admiration of Oden, Yamato often does things and considers certain actions based on assuming the identity of Oden himself. This led to Yamato being considered delusional by Luffy, Ulti, Shinobu, and Momonosuke. Kaido is Yamato's father and the two have a strained relationship, as Yamato idolizes Kaido's enemy, Kozuki Oden. When Yamato told Kaido of the desire to be Oden, Kaido responded with violent beating and has subsequently been cruel to Yamato numerous times since childhood, having kept Yamato imprisoned on Onigashima since the age of eight years old. He even had Yamato cuffed with explosive shackles to prevent a possible escape. Yamato originally had some doubts that they would explode, but after Luffy removed them and they did in fact explode, Yamato realized that Kaido was actually willing to kill his own child and, as a result, chose to sever relations with him, such to the point of proclaiming that there would not be any concern for Kaido if he were killed during the raid on Onigashima. Kaido's overall view of Yamato is unknown. Although, Yamato has emulated Oden for the past 20 years to the point of even dressing up as a man like him, and although Kaido disapproves of this idolizing of him, he does refer to Yamato as his son, in a way possibly respecting Yamato's desire be a man just like Oden was. However, Kaido does not seem to be aware that Yamato wishes to fulfill Oden's dream of opening Wano's borders, a cause which he is opposed to. Furthermore, though he has called Yamato an "idiot," he wished to have Yamato participate in his party during the Fire Festival and later announced across Onigashima his intention for Yamato to replace Orochi as shogun, showing that he places great trust in Yamato to assume such a position. After failing to set sail with Ace, Yamato had been waiting for his brother, Monkey D. Luffy, to arrive at Onigashima. For this reason, Yamato chased and clashed with Luffy after finding him, ignoring his time constraints in order to talk to him, even if for just five minutes. Yamato then trusted Luffy enough to request his help in achieving Oden's dream of opening Wano's borders, and then expressed a wish to be freed from Kaido and an intent to leave Wano with Luffy's crew as a means to be free and explore the sea like Oden did. Therefore, after Luffy removed the explosive handcuffs Kaido had used to imprison Yamato, the two decided they would fight Kaido together. Their trust has slowly grown and Luffy even entrusted Yamato to help them protect Momonosuke. Luffy refers to Yamato by the nickname "Yama-o", similar to the nicknames he uses for Trafalgar Law, Bartolomeo, and Eustass Kid. Yamato appears to not understand Luffy's use of nicknames, as evidenced by the attempt to correct Luffy with the former's actual name, as well as Ulti's name when Luffy gives her a nickname as well. Yamato met the pirate, Ace at some point in the past and had tried to sail out of Wano with him, but was kept prisoner on Onigashima, shackled with explosive handcuffs. Yamato seems to respect him, as evidenced by the conversation with Luffy in which Yamato fondly stated that Luffy was reminiscent of Ace and that, although it was not possible to set sail with Ace, it would be possible to leave with Luffy due to them being brothers.
Yamato is a very powerful warrior, with Black Maria noting that bringing Yamato back to Kaido's fortress after having escaped would be a difficult task. Yamato appears to have eaten a Zoan-type Devil Fruit. The exact animal species is unknown as Yamato has never fully transformed; however, before being interrupted, Yamato's teeth transformed into fangs when the transformation began. Yamato possesses monstrous strength resembling Kaido, being capable of wielding a large and heavy kanabo and using it to knock out Ulti, an Ancient Zoan user and one of the Tobiroppo, with just one blow. Yamato was also able to physically match Luffy's strength with relative ease, even when the pirate increased his strength exponentially with Gear Second and Gear Third. When Yamato countered a punch from Luffy with a kick, the powerful collision destroyed much of the surrounding wall and ceiling and blew back the Beasts Pirates around them. Luffy was even easily picked up and held with just one arm while running due to Yamato's stature. Yamato was later able to shatter the extremely tough armor and weaponry of the Beasts Pirates' Armored Corps with great ease. Yamato is quite fast, being able to lunge forward with blinding speed to attack, as well as outrun members of the Beasts Pirates in pursuit, and eventually completely elude the pirates and escape to the attic with Luffy without anyone seeing them. Yamato also possesses tremendous durability, having emerged from being struck by multiple explosive bazooka blasts with only superficial bruises and cuts, though eventually began taking more serious wounds as the bazooka strikes continued. Yamato wields a giant kanabo club much like Kaido, albeit studded and more slender, while Kaido's is spiked and a bit thicker. Coupled with Yamato's immense strength, the kanabo can wreak tremendous damage to objects and opponents with a single hit, and with Yamato's strength and Haki, it can be used to perform flying strikes that can even resemble energy blasts. In addition to the kanabo being a powerful blunt weapon, Yamato has masterful technique with it, being capable of moving it to counter Luffy's rapid attacks with little effort. Yamato is a user of Busoshoku Haki, as evidenced by them imbuing their hand and kanabo with it while preparing to attack Hatcha, resulting in a lightning-like effect. Yamato can use this Haki to an advanced degree, being capable of projecting it a great distance forward and hitting faraway opponents with tremendous force with a simple kanabo swing.
