Izo is the former commander of the 16th division of the Whitebeard Pirates. He is also the older brother of Kikunojo. Before becoming a member of the Whitebeard Pirates, he was a former resident of Wano Country, and the heir of his father's dancing school, Hanayanagi School in Ringo. Like Kiku, he is also associated with the Kozuki Family, namely Kozuki Oden, being one of his retainers. Izo is a cross-dressing man who wears a pink and purple kimono. He has a pale complexion and hair tied in a way resembling that of a geisha. He has a loose, long strand of hair that hangs over the right side of his face. He also carries another Japanese-looking, light-red spotted indument tied around his waist. After the timeskip, he is shown to have a small scar over his right eye, his hair appears longer, and he has second shorter strand of hair hanging over the left side of his face. During the Wano Country Arc, he wears a light-colored kimono bearing the simplified version of the Whitebeard Pirates' Jolly Roger with an added flame motif, as well as a dark cape. Izo also wears dark-colored gloves. When he was a child, he was seen dressing as a geisha, wearing a kimono with a diagonal spot design. He had the top of his head shaven, with his bangs parted and the back tied up and pinned. He was also seen holding Japanese fans and dancing. Izo is very loyal to the Whitebeard Pirates and Whitebeard, as he was willing to risk his own life in order to save Ace from execution during the Battle of Marineford.
Prior to joining the Whitebeard Pirates, Izo was loyal and very close to Kozuki Oden after he found both him and his younger sibling Kikunojo on the streets of Ringo dirtied and hungry. Even 20 years after Oden's death, Izo is still very loyal to him, having returned to Wano in order to take revenge on Orochi and Kaido. As a samurai, Izo appears to value a glorious and meaningful death in battle over his own life, stating that he missed the chance to have one too many times, and is therefore ready to lose his life in the raid against Kaido's dominion over Wano. Kikunojo is Izo's only sibling. After their father was arrested and convicted, they stayed together to survive in the streets of Ringo and they both joined Kozuki Oden. When Oden, Inuarashi, Nekomamushi, and Izo went missing, Kiku expressed worries as she could not find her brother and the others while crying. Later, when Nekomamushi and Inuarashi returned to Wano and informed Kiku about Izo staying with the Whitebeard Pirates, Kiku expresses positivity, knowing that her brother will be happy. During the raid on Onigashima, they reunited for the first time in over 25 years and he was pleased to see Kikunojo again. Before Izo joined the crew, he was cold towards Whitebeard when Oden’s life was in grave danger. After Oden officially joined the Whitebeard Pirates, his attitude changed as he became close with the crew. When Oden left the crew, Izo chose to remain and has been a member for more than twenty-five years and became the sixteenth division commander. He was willing to rescue any of his crew when he was at Marineford. Izo, like the rest of the crew, was saddened when Whitebeard and Ace died. Like the Nine Red Scabbards, Izo is one of Oden's closest confidants and retainers due to Oden taking him and his sister under his care during his journey around Wano. When Oden stubbornly tried to follow the Whitebeard Pirates in setting sail, Izo joined him. Even after twenty years since Oden's death, Izo is still extremely loyal to Oden as he would along with Nekomamushi assist the Nine Red Scabbards and Straw Hat Pirates in the raid on Onigashima to avenge his master's death.
As the commander of the Whitebeard Pirates 16th division, Izo has authority over the lower-ranking subordinates. Like the other commanders, he is very powerful. Izo is extremely adept with his pistols, especially in close quarters combat. With a single shot, he was able to break a sword in half as well as injure its owner by shooting it just moments before it slashed him. As the Scabbards prepared to attack Kaido, he is shown disarming King of his sword with a single shot. Dangirigan, literary meaning "Bullet Slicing Rounds"): After imbuing his bullets with Haki, Izo shoots his bullets in a manner that produces a flying slash-like barrier around each bullet, generating an attack that pierces and slashes his opponent at the same time. This attack was first used against Kaido in battle alongside his sibling Kikunojo. During his time in Wano Country, he was seen wielding a sword in order to assist Oden to fight against Ashura Doji. He was also seen carrying a sheathed sword by the end of the Battle of Marineford. Izo and his sibling, Kikunojo, were born in Wano Country. During their childhood, they were raised in a dancing school but their family was torn apart after their father was arrested. Afterwards, they had to survive on the streets in Ringo. When Kozuki Oden arrived and gave them food, they joined him. After Oden became daimyo of Kuri, he became one of his retainers. After Inuarashi, Nekomamushi, and Kawamatsu joined Oden, they were running low on funds. Therefore, he and the other retainers attempted to steal money from Yasuie, but they were caught. Instead of punishing them, Yasuie allowed them to take the money and encouraged them to use it to become better people for the sake of Oden and Wano Country. Following Yasuie's advice, they educated themselves and trained to become dignified warriors. 30 years ago, they visited the Flower Capital with Oden. Two weeks after the Whitebeard Pirates arrived at Wano, Oden secretly followed the crew when they decided to leave Wano at night secretly to prevent him from joining the crew. However, Izo knew Oden's plan beforehand and chased after him. He was pulled up after hanging onto Oden's body and tied up on the ship for at least three days before Whitebeard decided to let Oden join the crew. Soon after, his fellow comrades, Inuarashi and Nekomamushi, were discovered to have stowed away on the ship as well, having waited for Oden. After many adventures together, Izo was seen partying with the crew happily. After two years with the Whitebeard Pirates, Oden and Toki's son, Kozuki Momonosuke, was born and Oden received a bounty. Izo urged Oden to return to Wano for the sake of his wife and son, but Oden insisted on continuing with his adventures. Another two years later, the Whitebeard Pirates clashed with the Roger Pirates on an island for three days and three nights before the skirmish became a gift exchange. Oden decided to join Roger for one year to assist him with his final journey. Rather than go along with Oden, Izo decided that he preferred sailing with the Whitebeard Pirates and chose to wait alongside Inuarashi and Nekomamushi for Oden to return, but the latter two left him behind when they snuck onto Roger's ship without him. The Whitebeard Pirates learned about Oden's death several years after it happened. Some time over the course of twenty-four years, the crew expanded from five divisions to sixteen and Izo assumed control of the 16th Division as one of the Division Commanders. At some point after Ace became the 2nd Division commander, he talked about going to war with Kaido to liberate Wano Country, but Whitebeard never agreed to this request. Izo stated that he would join Ace once Whitebeard gave his approval.
