Once upon a time, a notorious pirate named Woonan hoarded one-third of the world's riches on an enigmatic island shrouded in secrecy. Presently, Luffy and his crew get robbed by a gang of thieves, under the leadership of the infamous El Drago, who are heading towards the same mysterious island that Woonan hid his treasure on. While recovering their stolen goods becomes a top priority for the Straw Hat Pirates, they are also interested in discovering the island's wealth and uncovering the story of the legendary pirate, Woonan.