He is a minor antagonist of the Long Ring Long Land Arc, and along with the other Marines, he is one of the main antagonists of the Marineford Arc.
Kuzan is an incredibly tall, slim and muscular man, roughly of the same size as the other two admirals Sakazuki and Borsalino, the latter clearly taller than Brook but it seems that he also is shorter than Doflamingo who is 305 cm (10'0") tall. He has black, curly hair cut to chin length that fans out at the tips, tanned skin and an altogether lean, long build.
His standard outfit while in the Marines consists of a white buttoned-up vest with standing collar over a long-sleeved navy blue shirt and matching white trousers and black dress shoes, rarely accompanied by a matching suit jacket. He also wears a yellow tie divided geometrically by black lines and a sleep mask on his forehead. During his preparations for the war against Whitebeard, Kuzan has a white Marine admiral's coat (golden epaulettes and for him being the ice user, blue cuffs) draped over him like a cape, as did the other admirals. He also is seen wearing a green and purple sleep mask at all times two years ago from the present timeline. In contrast to Borsalino and Sakazuki, Kuzan is far younger than his colleagues, being less than fifty years old; altogether, his looks, combined with his manner, make him appear even younger than he actually is.
As a child Kuzan had a grimace on his face. He wore a dirty light blue shirt and a purple pair of shorts with white stripes. He carried an umbrella tied on his back, a bottle of alcohol and a backpack. Also, his hair was curlier compared to his current hairstyle.
In his youth, Kuzan wore a white marine cap and a shirt.
Twenty-two years ago during the Ohara Incident, Kuzan wore a dark blue bandanna with a white Marine symbol on it, as well as a pair of black round sunglasses, as well as an indigo coat with the Marine emblem on the left chest and the back. This outfit was also what he wore 27 years ago, during the Battle of Edd War.
After the timeskip, his attire bears similarities to what he wore in his 20's. He wears a blue bandana and a dark blue trench-coat along with black pants and a white deep V-neck shirt. He also now wears black cowboy boots and travels with a knapsack carrying his belongings along with his old pair of green round sunglasses. He, like his rival Sakazuki, has also grown facial hair, namely, a thin mustache and a beard.
After his duel on Punk Hazard, Kuzan received several burn scars spanning from the right side of his neck down to his entire right shoulder and onto his torso. His right hand is also heavily scarred and most noticeably he's lost part of his left leg, for which he now wears a prosthesis made of ice formed from his Devil Fruit ability.
Kuzan is a very laid back man, showing no shock or surprise from almost anything. His lack of interest and "Lazy Justice" (as he describes his motto himself) often leads others to believe that he can not possibly be a marine of such a high ranking. However, if he deems a situation worthy, he will take action, as shown when he created a passage to another island for Tonjit at Long Ring Long Land.
In accordance with the age difference between him and the other pre-time skip admirals, Kuzan does not refer to himself with "Washi" , the "I" typical for older men but the "I" more frequently used by younger men and teens, the rather rough "Ore" altogether, his speech style is far laxer than that of Borsalino (who speaks exceedingly polite), containing a lot of ellipses and contractions, yet lacking the rude connotation of Sakazuki's speech, and being far calmer than that. He tends to begin addressing people with "excuse me"/"I hate to interrupt, but…"
He appears to be the most benevolent of the three pre-timeskip admirals, helping Tonjit at Long Ring Land to cross the ocean with the power of his Devil Fruit and even letting Nico Robin escape the Buster Call on Ohara. He seems to dislike the Shichibukai, or at least Crocodile, as he said that the only reason he did not kill Luffy was that Luffy had defeated Crocodile.
In contrast to his former colleague, Fleet Admiral Sakazuki, Kuzan has a sense of honor, as he keeps his word to not attack the Straw Hat Pirates after accepting a one-on-one battle with Luffy. Kuzan's moral stance is unknown, but it is likely that he follows Moral Justice. He is disgusted by Sakazuki's brutal actions in dealing with situations (such as the Ohara Incident), calling him a fool. While he may follow Moral Justice, he does understand the position his ranking puts him in, as he does not hesitate to do what is necessary for the needs of the Marines, as shown when he freezes Jaguar D. Saul after the Ohara incident, and attacked Luffy and Whitebeard during the Marineford War.
Aokiji was a faithful follower of the World Government. He always tried to follow orders but sometimes found his own ideals in opposition to his orders. Even as he followed his orders, he would sometimes exhibit a sense of mercy and honor that other World Government officials did not. Like many characters in One Piece (for example, Jaguar D. Saul and Smoker), after witnessing the senseless murder of many innocent people, Aokiji may have come to realize the depths to which the World Government will sink to accomplish their goals.
His relaxed demeanor while performing the more macabre of his duties is similar to that of Borsalino, making him one of the more complicated characters in the series. Despite not really wanting the position of fleet admiral, he was even more opposed to Sakazuki getting the position, and dueled his fellow admiral rather than letting him take it. After being defeated, Kuzan chose to resign from the Marines rather than stay under Akainu's command.
Aokiji during the Whitebeard War at Marineford grudgingly shredded his usual lax and friendly nature, for a more ruthless and aggressive personality, repeatedly targeting Whitebeard himself with his Hie Hie no Mi, managing to severely injure "Diamond" Jozu and generally hampering any attempts at rescue or escape for the invading pirate fleets.
After the timeskip, having left the Marines and realizing just how truly corrupt the world is, government and military, it becomes clear that Aokiji seems to be only looking after his friends illustrated by his rescue of Smoker from Doflamingo's fury on Punk Hazard.
He has a recurring phrase, "Arara", meaning "Oh, my", which is frequently used when something surprises him.