The 18th Branch in the East Blue... This is the most peculiar branch of the Marines, built in the East Blue, known as the weakest sea, yet it is more magnificent than the headquarters. Could the Summit War actually take place in a branch? A branch prison replaces Impel Down? The East Blue has even entered an era without pirates? ... Soon, everyone discovers that, without realizing it, even the Marine headquarters is on the verge of losing its significance!