He is one the most feared antagonist in the story. Sakazuki, also known as Akainu which means "red dog" is the current fleet Admiral of the marines. He rose in becoming the fleet admiral by beating admiral Kuzan in a ten day battle in Punk Hazard. The fierce battle, although not shown made drastic change in the climate of the island of Punk Hazard. After succeeding former fleet admiral Sengoku in the position he made numerous changes in the marines one of it was the relocation of marine headquarters in the new world to prepare for the upcoming new age of pirates.

Sakazuki entered the marines at the age of 23 and was a student of admiral Z both he and Borsalino were called monsters based on the One Piece Film: Z. He was also seen at the buster call at Ohara together with Kuzan (Like Sakazuki, a Vice-Admiral at that time) and Vice - Admiral Saul. He is an extremist and blind follower of Absolute Justice, he believes that every threat must be annihilated that's why under no circumstances he tried to kill Luffy during the war at marineford. 

Being the fleet admiral of the marines he has the power to rule over the lower ranking marines. Also, he has the power of Haki as stated by doctor Fishbonen that all vice-admiral possesses the power of Haki. Sakazuki ate the Magu - Magu no mi which is a logia type devil fruit. The Magu - Magu no mi is so powerful that it is even superior to the Mera - Mera no mi. After the two year time skip it is still unknown if his strength greatly improve or that his devil fruit ability is awakened.

Sakazuki's character is based on the actor Bunta Suguwara and his nickname was based on Momotaro Legends where the other two admirals also got their nickname namely admiral Borasalino and former admiral Kuzan.