The Straw Hats take a vacation at Spa Island, but while there, encounter Foxy and his crew, who are pursuing two small girls: Lina and her older sister Sayo. The Straw Hats manage to defeat the Foxy Pirates, and learn that they had been pursuing Lina and Sayo for the girls' notebook, which shows their father's research on how to create a special gem, the solution for which can be found on the island. Lina considers her father a liar, but Sayo believes him. Suddenly, Sayo is abducted, and the owner of the island, Doran, says that if they want her back, they must complete the research and find the gem.