Koala is a former slave who was set free by Fisher Tiger's rampage on Mariejois. She sailed along with the Sun Pirates to reach her home town. At some point later, she became the Fishman Karate assistant instructor of the Revolutionary Army, where she now works with Sabo, making an appearance in the Dressrosa Arc. When she appeared twelve years ago, Koala was a skinny girl with long, unkempt brown hair. She also had distinctively large and round eyes, similar to that of a koala, and was always smiling. She had on a dirty, short-sleeved collared shirt, which she wore under dark overalls and a smudge on her right cheek. Judging from the way Fisher Tiger branded her on her back, she had the mark of the Celestial Dragons on her back, which was replaced by the mark of the Sun Pirates. After a few weeks she had neat, shoulder-length hair, a light-colored dress, and a pair of loafers.
At age 23, she became taller, slim, curvaceous and extremely well-endowed, with a pronounced hourglass figure, and wears a crimson newsboy cap with gold goggles, a pink shirt with frilly collar, a maroon short skirt, and black thigh-high stockings with brown boots. Aladdin described Koala as having the lifestyle of a slave ingrained in her blood. Even after being set free for three years, she was very apologetic and vowed to never cry or stop working. The pirate explained that if a slave ever cried or stopped cleaning, then they would be killed. Koala seemed to consider the Sun Pirates her masters, as she asked them if she would be killed if she stopped cleaning. The pirate also said that slaves panicked constantly, even when they were by themselves, and could never trust anyone. It is unknown if Koala also became paranoid in that regard. But when Fisher Tiger convinced her that they were not like the Celestial Dragons by throwing a gun into the water, she finally cried for the first time in years. She then began to regard the Sun Pirates as her family rather than her masters, though this did not stop her habit of cleaning even when she wasn't asked. By the time they reached her home town she genuinely liked the fishmen and mermen of the Sun Pirates, creating especially strong bonds with Hatchan and the future members of the Macro Pirates. She went as far as to actually hold Fisher Tiger's hands despite him trying to shake her off. At the age of 23 Koala has become much more mature, having shown compassion to Sabo for not being there to save Ace and that he should not let his guilt get to him.
She also has become rather playful and cheery, having gleefully hugged Robin again after meeting her and teased Sabo about him crying upon meeting Luffy again. She has also been shown to have a temper, as she got angry with Sabo for fighting Fujitora instead of staying at his post and comically pinched his cheeks for his disregard for his duties as a Revolutionary. Koala's only known family is her mother. It is clear she loves her mother very much, having hugged her after reuniting with her when Tiger brought her home. It is unknown if Koala ever discovered of her mother and the other people on her home island betraying Tiger by selling him out to the Marines. She's been shown to have certain skills like being able to take down larger enemies and great agility and can make a big jump from the stands to all the way down to an underground port while bringing Sabo clothes to wear. Her position indicates that in terms of combat, she is above simple revolutionary soldiers, as she seems to have a decent level within fishmen standards despite being human. She is skilled enough at Fishman Karate to be able to teach it and was able to defeat an opponent much larger than her. Not being a fishwoman and still being able to learn the art makes her more impressive. In the anime, she is shown to be proficient enough to defeat a group of five armed men with only a single strike each. After Fisher Tiger attacked Mariejois, Koala escaped and fled to an island. Unfortunately, the inhabitants there had no way of returning her to her homeland. When the Sun Pirates visited there three years after she was freed, the inhabitants asked them to take the little girl home. After Koala introduced herself and thanked Tiger for freeing her, she boarded the Sun Pirates' ship. Koala was instantly met with hostility by Arlong, who hit her for being human, but was restrained by Hatchan. Tiger gave the girl the mark of the sun to cover up her slave mark. He then told the girl that she was allowed to cry if she wished and made a vow to return the little girl to her home. Koala then began to cry. The Sun Pirates were able to find an Eternal Pose for her home island, Foolshout Island. When they arrive, she bid everyone farewell, and Tiger took her to her village. The whole town rejoiced, but everyone was still afraid of Tiger. Later, she heard some strange noises. When she asked if anyone else heard them, her mother replied no. The truth was that Fisher Tiger was attacked because people from a previous island informed the Marines about the Sun Pirates while the people on this island allowed it on the condition that the Marines overlook the fact that she was a released slave and not take her back. Three years after Fisher Tiger's death, Koala joined the Revolutionary Army and she became a Fishmen Karate assistant instructor. She became acquainted with Sabo and Hack. She was worried when Sabo had a mental breakdown after remembering his brother, Ace. When Sabo awoke from his three-day coma, Koala cried in relief. After Robin agreed to meet Dragon, Koala became acquainted with her. After returning to the revolutionary base at Baltigo, Koala informed Dragon that the weapons they retrieved from Dressrosa contained a special mineral known as Liquor Iron Ore, which could provide a clue on where the weapons were made. After a short conversation concerning Luffy, Sabo, and Robin, Dragon requested Koala to gather all the revolutionary leaders.