One Piece: Umi no Heso no Daibouken-hen

Unlike the other specials, this story takes place in an alternate reality version of 19th century Japan, in "The Grand Jipangu", an alternate version of The Grand Line as opposed to simply being hour-long filler episodes.The story is divided into two halves: in the first, Buggy the Clown makes trouble in the town where Detective Luffy is stationed, and in the second a mysterious girl named Vivi appears. These stories feature cameos from several minor characters in the normal series. Surprisingly the "Oyabun" (Boss) specials did not stop there as five more specials were made following the first one, mostly as Christmas and New Years specials as well as fillers once in awhile.

The story opens on Pirate Zap's ship, where two of his crew, Bonnie and Max, are tired and want to escape, but unfortunately they have no money. Three children were being held captive on the ship overhear them. The eldest, Amanda, who's father was a pro treasure hunter, knows the whereabouts of a great treasure, and offers them a deal. If they help them make a clean escape, they could take all the treasure they wanted. They agree, and the five of them barely escape and make it onto a small island where they meet Luffy and his crew. Unfortunately they were pursued and Luffy and Amanda are captured and brought back to their boss, the head of the Bayan Pirates, who is also after the treasure. Now Luffy and the others must battle the Bayan pirates and find the treasure that Amanda's father had left for his children. Amanda, who has always resented adventure and treasure because her father was constantly gone in search for it, finally understands his feelings.

The Straw Hat crew obtain an advertisement for a recreational island on the Grand Line run by the Baron Omatsuri. Luffy decides to take this opportunity to kick back and relax. Unfortunately, when they arrive at the island, they are asked to compete in contests through unity for access to relaxation. However, there seems to be a mysterious air on the island, as the Straw Hat Pirates begin to fight amongst themselves, while Robin, Chopper, and Luffy individually search for the secret behind Baron Omatsuri's island.

The special will be a completely new work, featuring reanimated scenes from the beginning of the series through when the crew enters the Grand Line. The special is commemorating the manga's 20th anniversary, and will also feature anime versions of the original manga's chapter cover stories as part of the special's ending credits. The staff haven't yet clarified which cover story or stories will be animated. Additionally, the anime will feature a special 20th anniversary commemoration version of the original opening theme song "We Are!".