As an artificially-created ancient giant, Jaki is immensely bigger than the vast majority of people, although among the Numbers he appears to be relatively short. He has a rotund physique with disproportionately short legs and little neck area between his head and torso. He has a wild mane of light hair that almost reaches down to the ground. He has a very small round nose and a mouth with large and sharp teeth; his two upper canine teeth are much longer and notably curve to the sides, resembling tusks. He also has a pair of broad, light-colored horns on his head which curve upward like a bull's and point toward each other. The only piece of clothing he appears to wear is a short, raggedy loincloth with dark patterns on it. On the right side of his exposed chest, he has a tattoo of Daiji 肆, which means four.
Like many of his fellow Numbers, Jaki is a rowdy drunk and was considerably intoxicated when fighting broke out on Onigashima. Like the other Numbers, he has a unique laugh that is based on his name: "Jakikiki".
Abilities and Powers
As a failed ancient giant creation, Jaki has significant physical power to complement his size, as shown by his ability to wield his massive club as well as carry the Brachio Tank V with only one hand. However, he was quickly taken down after being struck in the face by Franky's Radical Beam.
Over 20 years ago, Jaki was a subject in an experiment on Punk Hazard that attempted to recreate the ancient giants. The experiment was a failure, but Jaki and his fellow test subjects were recruited by Kaido. They began residing on Onigashima and joined Kaido's crew, the Beasts Pirates, as a group called the Numbers.
After the events of the Legendary Hour, Jaki was among the pursuers of the Nine Red Scabbards, who were escaping from Kaido's forces following Kozuki Oden's execution. He was able to catch both Inuarashi and Nekomamushi, who were distracted arguing with each other.
Four Emperors Saga
Wano Country Arc
During the festivities on the day of the Fire Festival, the Ninja-Pirate-Mink-Samurai Alliance unleashed a surprise assault on the Beasts Pirates. At some point, Jaki, Juki, and Goki encountered Usopp and Chopper inside the Brachio Tank V, and Jaki easily picked up the contraption. The trio of Numbers then arrived at the Live Floor to fight the rebels, and Franky fired a Radical Beam in Jaki's face to free the Brachio Tank while also defeating Jaki after said attack. Soon afterwards, a still-unconscious Jaki was picked up by Hatcha, who carried him over his head.
- One Piece Manga and Anime — Vol. 95 Chapter 954 (p. 14) and Episode 955, Jaki is seen in silhouette with some of the other Numbers.
- One Piece Manga — Vol. 98 Chapter 989, Jaki is named and seen in full.
- One Piece Manga — Vol. 96 Chapter 973 (p. 5), Jaki captures Inuarashi and Nekomamushi.
- One Piece Manga — Vol. 98 Chapter 991.