You see a reunion between 4 powerful siblings, Luffy the captain of the Straw Hats and future Pirate King, he is also the user of the Nika Fruit, a devil fruit with the power of the Sun God which makes the user's body have rubber-like properties, Ace the captain of the Whitebeard Pirates who took over after Whitebeard's death and a last minute save from Uta, Ace is also the biological son of the now dead previous Pirate King Gol D. Roger, he doesn't like anyone to talk about it, he is also the user of the Flame Fruit, Sabo, the son of some rich people who hates his blood family, unlike the others he's not a pirate despite wanting to be one but rather he's the 2nd-in-command of the revolutionary army and last but not least is their sister Uta, she was adopted by Shanks but was raised by Garp alongside Luffy, Ace and Sabo, she is a famous Pirate Musician with the Sing Fruit