ONEPIECE 3D2Y

The special takes place during the two year before the Straw Hats reunite on Sabody. Luffy is currently in Rusukaina training to get stronger to take on the New World. However the training is interrupted when Hancock's sisters, Marigold and Sandersonia, are kidnapped by the Byrnndi World, a pirate who was locked away on Level 6 of Impel Down but escaped during Luffy's invasion to save Ace, in order to lure Hancock to him and use her as a hostage against the World Government due to her Shichibukai status. Thus Luffy and Hancock head off to confront him and save Hancock's sisters.

Rayleigh, Hancock and Nyon manage to find Luffy and revive him. Hancock naturally wants to go save her sisters and Luffy decides to tag along despite objections from Rayleigh since he's still in the middle of training. He eventually agree though only after Luffy promises not to make too much of a scene to keep himself hidden from the Marines.