Summary:
The interior of the Rainbow Mist is full of shipwrecks and treasure and is guarded by five children. The children are actually friends of Henzo, who got lost in the fog over 50 years ago.
Inside the Rainbow Mist (a mysterious mist that is a portal to another dimension), Henzo and The Straw Hat crew, except for Sanji, Nami, and Chopper, arrive at Ape’s Concert, a pirate ship graveyard in the Rainbow Mist. Robin explains that here beyond the Rainbow Mist is a land of eternity with untold treasures, where all its inhabitants never age. Luffy brings a treasure chest aboard the Merry and tells everyone that there is much more to the wrecks. A mysterious voice threatens the crew with the curse of the dead unless they return the treasure and leave immediately. Then the ghosts suddenly appear and shoot an arrow that almost hits Zoro. Luffy attacks the ghosts and discovers that they are actually children trying to scare off all the intruders. A boy named Rapanui announces that they are The Pumpkin Pirates and demand that the Straw Hats leave or they will set off a bomb. Henzo recognizes Rapanui and the other children and explains who they are, they are very old friends. Henzo tries to prove that he is trying to detonate the bomb the Rapanui is holding, saying that it is just a “Ka-boom Mark 3”, Henzo’s invention that only fools the opponent. Rapanui sets off a smoke screen and all the children disappear.
As a flashback, Henzo explains to everyone how years ago (as a child himself) the Pumpkin Pirates dreamed of becoming real pirates and recounts the time when their town of Ruluka was attacked and set on fire by The Wetton Pirates. The kids flee the city by stealing a Pirate ship while Captain Wetton and his crewmate Ian give chase. As the kids fight Wetton and Ian, Wetton and Henzo fall overboard and the rest of the kids sail straight into the Rainbow Mist, never to return. Realizing that the Rainbow Mist has prevented the children from aging, the crew tries to find a way out of the Monkey Concert.
Back in Ruluka town, Sanji continues to fight Lake, the grandson of the town’s mayor, Wetton, for not paying port taxes to the town. The coin hits Lake in the head, knocking him out. He asks Sanji if he was the one who threw the coin at him, so Sanji, Nami, and Chopper decide to lie and say that he was. Lake picks up the coin and takes it as payment for the tax for docking their ship in the city’s harbor and formally welcomes them to the city. They continue to the port and look for the rest of the crew. Lake tells them that The Going Merry was last seen heading to the Ape’s Concert behind a strange fog in the ocean where the ship graveyard is. He tells them that the mayor has announced that all the shipwrecks there have intact cargo of gems and coins and tells them that Henzo is employed by the government to research how to safely enter the Ape’s Concert. Nami tells Sanji and Chopper that they need to go inside to find their friends and hopefully the treasure. Mayor Wetton then arrives and chastises Lake for saying too much, telling them that no one is allowed inside the Rainbow Mist without his permission.