One Piece had one of its most controversial character arcs when former Marine Admiral Kuzan rose as the tenth Titanic Captain of the Blackbeard Pirates. The ice-wielding powerhouse renounced his military career and moral compass to operate under one of the series' most ruthless antagonists. This partnership disregarded every expectation about justice and loyalty in the series.
Kuzan joined Blackbeard because his loss against Akainu ravaged his faith in Marine justice, while Blackbeard's proposal of freedom and friendship offered a getaway from institutional corruption. The former Admiral's decision emanates from his traumatic experiences at O'Hara and his growing disillusionment with the World Government's methodologies. His coalition likely serves dual drives: genuine camaraderie and a covert mission to monitor Blackbeard's dangerous activities.
The events following the Marineford War marked a turning point in One Piece's history. Fleet Admiral Sengoku's retirement created a power vacuum that led to a brutal succession battle. Kuzan and Akainu engaged in a devastating ten-day fight on Punk Hazard to determine the next Fleet Admiral.

Akainu's victory came at a tremendous cost. The battle destroyed an entire island and left both combatants severely injured. Kuzan lost his left leg in the battle, but what truly broke him was losing trust in the Marine system after Akainu took command.
The Ohara incident serves as the foundation for understanding Kuzan's motivations in One Piece. As a young Marine, he participated in the Buster Call that destroyed the island of scholars. This traumatic experience introduced him to his close friend Jaguar D. Saul, whose sense of justice differed greatly from standard Marine doctrine.
Losing Saul in that event deeply changed how Kuzan sees the world. The giant's final words about protecting Nico Robin resonated with the future Admiral. Kuzan began carrying out Saul's will by secretly helping Robin survive throughout her childhood and teenage years.
Meeting Blackbeard: A Fateful Encounter in One Piece

Following his exit from the Marines, Kuzan wandered aimlessly until his journey brought him face-to-face with Marshall D. Teach. The encounter took place in a bar where Kuzan shared his story about the fight with Akainu and his subsequent departure from the organization.
Blackbeard's crew initially suggested stealing Kuzan's Devil Fruit powers, but their captain had different plans. Instead of viewing the former Admiral as prey, Blackbeard extended an offer of friendship and asked him to become the tenth Titanic Captain of his crew in One Piece.
The pirate captain's ideology about his crew being "just friends sailing together" appealed to Kuzan's desire for freedom. This casual course to piracy contrasted sharply with the rigid ranking and absolute compliance demanded by the Marines under Akainu's leadership.
The SWORD Connection Theory

Clues suggest that Kuzan still has connections with SWORD, the Marines' covert ops unit in One Piece. His connection with Garp, who likely plays a considerable role in SWORD's operations, endows this theory. The two veterans appeared on Water 7 simultaneously, possibly for a clandestine meeting.
Kuzan's rescue of Smoker on Punk Hazard raises questions about his information sources. His claim that "fate" brought him to the island seems insufficient to explain his precise timing. Communication from SWORD operatives provides a more logical explanation for his knowledge.
If Kuzan operates as an undercover agent, his mission involves collecting intelligence on Blackbeard's activities. This dangerous task requires someone with the strength and cunning to survive among the most ruthless pirates. Only a select few are qualified to handle a mission this critical.
Kuzan's true purposes likely extend beyond simple espionage in One Piece. His experiences with corruption in the World Government have motivated him to seek fundamental change in the world's power structure. This goal aligns him with other revolutionary figures like Monkey D. Dragon.
The former Admiral's unique role allows him to work toward righteousness via anomalous means. Rather than trying to reform the Marines from within, he can gather proof of corruption and criminal activity from the outside. This strategy might work better than the usual ways of doing things.
In conclusion, Kuzan teaming up with Blackbeard in One Piece hints at deeper motives and layered intentions. The former Admiral's ultimate fate rides on successfully balancing his competing burdens. His eventual actions will presumably play a key role in defining the outcome of the war against the World Government and the fate of the series’ world itself.