Kuzan, more widely known by his former海军代号青雉， is a complex figure whose journey from one of the Marine's highest-ranking officers to a member of the Blackbeard Pirates places him in a unique gray area within the world. He is a tall, languid man, easily recognized by his dark skin, curly black hair, and the green eye mask he wears on his forehead, a tool for his famously sleep-loving nature. Standing nearly three meters tall, his appearance often belies his immense power and sharp intellect. Originally hailing from the South Blue, he joined the Marines at the age of nineteen and rose through the ranks, becoming a protégé of the legendary hero Monkey D. Garp and a student of the former instructor Zephyr.

His personality is defined by a deep-seated paradox. On the surface, he is the epitome of laziness, operating under a personal philosophy he calls "Lazy Justice". He is often seen nonchalantly napping or cycling across the frozen sea on his bicycle, speaking with a casual drawl and a recurring, surprised exclamation of "arara". This relaxed demeanor, however, masks a man of strong convictions who has been deeply troubled by the nature of justice and the World Government's actions. He initially burned with "Flaming Justice" as a young man, but a pivotal event shattered this idealism. During the destruction of Ohara twenty-two years ago, he witnessed fellow Marine Sakazuki (later Akainu) order the sinking of a civilian evacuation ship to ensure no scholars escaped. This act of absolute ruthlessness led Kuzan to abandon his fiery passion for a more detached, contemplative stance, adopting "Lazy Justice" as he resolved to observe the world rather than aggressively impose his will upon it.

His motivations are deeply personal and stem from this crisis of conscience. The Ohara incident created his most defining relationship: a silent pact with Nico Robin. Disobeying orders, the then-Vice Admiral Kuzan allowed the young archaeologist to escape, freezing the pursuing Navy ships and providing her a route to safety. He justified this act as a favor to his dear friend, the giant Vice Admiral Jaguar D. Saul, who had sacrificed himself to protect Robin. From that day forward, Kuzan watched over her from a distance, not as a protector, but as an observer, warning her that he would be the first to come for her if she proved to be a threat. He saw her survival as a test of Saul's dying belief that she could find her place in the world.

His role in the larger story is that of a wandering moral compass, challenging the black-and-white views of both pirates and Marines. As one of the three Marine Admirals, the World Government's "Greatest Fighting Force," he first confronted the Straw Hat Pirates on Long Ring Long Land. There, he effortlessly defeated the crew, but spared their lives, claiming it was repayment for their defeat of the Warlord Crocodile in Alabasta. During the Summit War of Marineford, he fought alongside the Marines to execute Portgas D. Ace, engaging in devastating clashes with the Whitebeard Pirates, freezing the ocean to stop tidal waves and impaling the infamous pirate commander "Diamond" Jozu.

The most significant turning point for Kuzan came in the aftermath of the war. He was nominated for the position of Fleet Admiral by the retiring Sengoku, but the World Government's higher-ups favored the more aggressive Sakazuki. Kuzan was vehemently opposed to Sakazuki's brand of "Absolute Justice," which he found fanatical and cruel. Their dispute could not be resolved diplomatically, leading to a legendary ten-day duel on the deserted island of Punk Hazard. The battle was so cataclysmic that it permanently altered the island's climate, leaving one half a burning hellscape and the other a frozen wasteland. Kuzan lost the fight, losing his left leg in the process, and rather than serve under Sakazuki, he chose to resign from the Marines.

After his departure, Kuzan became a wanderer, operating outside the law. He resurfaced to save his old friend, Vice Admiral Smoker, from the Warlord Donquixote Doflamingo on Punk Hazard. It was later revealed that he had formed an alliance with one of the Four Emperors, Marshall D. Teach, also known as Blackbeard. Kuzan became the captain of the Tenth Ship of the Blackbeard Pirates, a decision that shocked the world. His motivations for joining a crew he once would have hunted remain ambiguous. He told Smoker he had not changed, but now as an "outside observer," he could act more freely. He explained to Blackbeard that he wished to start living for himself instead of for others, suggesting a deep-seated resentment for the restrictions of his former life.

As an enemy of the World Government now aligned with pirates, his development showcases a man who has shed all institutional allegiances to pursue his own enigmatic agenda. He remains a man of honor, showing respect for his former teacher Garp even as their paths force them into conflict. In terms of ability, Kuzan is an exceptionally powerful fighter. He is a master of both Armament and Observation Haki. His primary power comes from the Hie Hie no Mi, a Logia-class Devil Fruit that allows him to become, create, and control ice at will. This power allows for a vast array of offensive and defensive techniques, from creating weapons like ice sabers and spears to unleashing massive, area-wide freezing attacks like "Ice Age," which can instantly freeze an entire ocean bay. While his ice body can be broken, he can reform himself, and he famously used his power to freeze the sea solid, allowing him to travel anywhere by bicycle. His defeat by Sakazuki's magma, a natural counter to ice, highlights the elemental weaknesses even top-tier Logia users possess, but his ability to fight on equal terms for ten days cements his status as one of the most formidable characters in the world.