Sakazuki, once known by his admiral alias Akainu, currently holds the position of Fleet Admiral within the Marines, succeeding the former Fleet Admiral, Sengoku. In the earlier part of the series, he served as one of the three admirals, being the last of the trio to make his debut. Upon assuming the role of Fleet Admiral, one of Sakazuki's initial decisions was to relocate Marine Headquarters to the New World, anticipating the onset of the New Pirate Age. In the manga, Akainu's name was initially mentioned by Nico Robin during the initial encounter with Aokiji. Meanwhile, in the anime, Vice Admiral Jonathan made reference to him earlier during the anime-exclusive G-8 Arc, which aired after Akainu's introduction in the manga. Throughout the series, Sakazuki stands out as an uncompromising advocate of Absolute Justice, to the extent that his extreme beliefs led Admiral Aokiji to oppose his promotion to Fleet Admiral, ultimately leading to Aokiji's resignation from the Marines after his efforts failed.
Due to his actions, Sakazuki emerges as one of the principal antagonists during the Marineford Arc, alongside Sengoku and Marshall D. Teach, and continues to play a prominent antagonistic role in the Final Saga following his promotion. Sakazuki possesses the powers of the Magu Magu no Mi, a Logia-type Devil Fruit that grants him the ability to generate, manipulate, and transform his body into magma. His magma is incredibly scorching and explosively potent, rendering it exceptionally suited for combat. This enables Sakazuki to incinerate, liquefy, and obliterate obstacles in his path, establishing his Devil Fruit as one of the most formidable in terms of offensive capabilities. In combat, Sakazuki primarily employs his magma-infused arms to deliver searing punches or clawed strikes, capable of penetrating even the toughest adversaries. He can also dramatically enlarge his arms to hurl colossal magma fists towards distant targets or unleash multiple magma fists, resembling a volley of meteor-like projectiles that wreak havoc on the battlefield. Additionally, he has been observed crafting his magma fist into the shape of a fanged dog head, a nod to his associated animal motif. Beyond the imperviousness conferred by his magma body against all but Haki-based attacks, the intense heat emanating from Sakazuki's form acts as a potent deterrent against adversaries attempting physical strikes, as they risk being severely burned. Moreover, his abilities grant him remarkable agility; he can melt through various obstacles, including solid ground, and briefly attain flight by propelling himself with jet bursts of magma. Even within the realm of Logia powers, Sakazuki's capabilities exhibit exceptional potential and devastating might. Prolonged use of his abilities over ten days resulted in the transformation of an entire island's climate, permanently converting it into a blazing inferno that extends to the surrounding sea. During the clash between Blackbeard and Law, Sakazuki awaited the outcome but expressed frustration over the duties of being Fleet Admiral. Subsequently, he received intelligence regarding recent events on Egghead Island, pondering the possibility of Vegapunk discovering his potential assassination by CP0 and its implications for the Marines' combat capabilities should Vegapunk align with the Straw Hats. He also received word of Kizaru's approach to Egghead and directed his subordinates to instruct CP0 not to engage the Straw Hats until the arrival of Kizaru and the Marine forces.
