One Piece "3D2Y": Overcome Ace's Death! Luffy's Vow to his Friends

Set during the two years before the Straw Hat crew reunites at Sabaody Archipelago, this special follows Luffy as he trains on Rusukaina Island to become stronger for the challenges of the New World. His training is interrupted when Boa Hancock's sisters, Marigold and Sandersonia, are kidnapped by Byrnndi World, a pirate who had been imprisoned on Level 6 of Impel Down but escaped during Luffy's attempt to rescue Ace. Byrnndi World kidnaps the sisters to lure Hancock and use her as leverage against the World Government because of her position as a Shichibukai. In response, Luffy and Hancock set out together to confront Byrnndi World and rescue her sisters.