The specialist treasure hunter calling herself Cherry lures Lupin to an "underground" auction of some treasure of the great pirate Zeke Barbatos who was active in Brazil 75 years ago. The treasure reportedly included the Jet-Black Diamond and Venus Ruby. At the auction, Lupin encounters an elderly woman who buys a kokeshi doll similar to his own which is part of the treasure. Lupin steals it and then returns it to the woman after extracting her scrap of Zeke's treasure map, but Fujiko swipes the pieces to track down the Jet-Black Diamond herself...