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.
One Piece "3D2Y": Overcome Ace's Death! Luffy's Vow to his Friends streams on cinevo in the best quality we can source for it, with subtitles in dozens of languages. Playback works in any modern browser on phones, tablets, laptops and smart TVs, and your position is remembered across devices.