From the Super Mario Wiki
When the player decides to stop here, he or she will meet Akiki, who is panicking over her missing Uncle, Ukiki. Her quest, Monkeynapping!?, is a mystery, for Shroomlock appears to assist. After Akiki gives Shroomlock a parchment involving Ukiki's disappearance, Shroomlock asks the player to try and locate him. Then, the player must go to Loch Dorrie to find Ukiki. If the player solves the mystery, he or she will be rewarded with the Gaddget Mini Maze.