This arc happens after the Wano Arc, and don't take it seriously. It is purely fan-made.
After the events of Wano, Kaido is defeated, for now. Monkey D. Luffy and his crew have a different goal in mind. Going to an island far away- Frabara Island. At this island, there are poneglyphs reading who they need to find to tell them where the One Piece is- Shanks. Shanks is busy somewhere in the New World but these poneglyphs can tell them where his location is. Also, the only way to get Shanks to tell them is with the Golden Key, a relic found on the island. Unfortunately, to get to Frabara Island, you need to go through the Air Stream. The Stream can be accessed by getting three cubic relics that are guarded by the Three Kings of West Blue. The Straw Hats will have to defeat them.
The First Member they fight is the second strongest member, Urako. His Devil Fruit, the Ningyo Ningyo no Mi, is a Paramecia that allows him to create puppets and control their body structures. These powers defeat all of the Straw Hats, except Monkey D. Luffy, who uses a Jet Gatling Gun to finish off Urako and get the relic. The next member they fight is the weakest one of them all, Dinno. Dinno proves a challenge with his Heri Heri no Mi, a Logia type that allows him to create, manipulate, and become helium. He is defeated from exhaustion and the Straw Hats get the relic. The Straw Hats are exhausted too, and that gives a chance for the strongest member, Terro, to capture them with his Zoan Fruit the Buru Buru no Mi, Model: Ox. They are trapped in a prison, but they still have the two relics because they hid them from view. The Straw Hats escaped and defeat Terro, getting the final relic and going through the Air Stream to Frabara Island.
At The Island
Once the Straw Hat Pirates reached Frabara Island, they were greeted by King Tyderleman. The King asked the Crew if they fought Seven Warlord of the Sea Member Silverbeard, and they said yes. The King told them that he was born here and that he was a problem. The King also gave them honorary passports because of them defeating Silverbeard, which allowed them to go past the Three Kings when they showed them these passports and go to the Air Stream. Then, the King told them where the poneglyphs were. But right when they saw it, Fleet Admiral Sakazuki came in to stop them from getting the One Piece. King Tyderleman tried to help with his unnamed Leaf Logia, but he was nearly killed. Fleet Admiral Akainu defeated the Straw Hats but had a stroke (Not Joking), so he could not fight. Then, the Straw Hats finally got the key and left the island to find Shanks, who helped them find the One Piece, but that's a different arc after this one.