That Time I Got Reincarnated as a Slime the Movie: Tears of the Azure Sea

With the help of the "Dragon Sin of Wrath" Meliodas and the worst rebels in history, the Seven Deadly Sins, the "Holy War", in which four races, including Humans, Goddesses, Fairies and Giants fought against the Demons, is finally over. At the cost of the "Lion Sin of Pride" Escanor's life, the Demon King was defeated and the world regained peace. After that, each of the Sins take their own path.

In the chambers of the Edo harem, two newcomers uncover political intrigue, rivalry and a vengeful spirit only one traveling medicine seller can vanquish.

One fateful summer, a group of elementary school kids set adrift on an abandoned apartment building must look within themselves to find a way back home.

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.