As a child, Monkey D. Luffy dreamed of becoming King of the Pirates. But his life changed when he accidentally gained the power to stretch like rubber…at the cost of never being able to swim again! Years, later, Luffy sets off in search of the "One Piece," said to be the greatest treasure in the world...

With the epic Paramount War now over, the scene shifts back to when a young Luffy first met Ace. Luffy, Ace and their friend Sabo get into all types of trouble as they grow up in a tumultuous time. Then, back in the present, Luffy will need to find the strength to recover from the loss of his brother.