Location: Water Seven City Area
Petitioner: Crybaby Hien
Reward: Yagara's Lost Item, 500 Berries
Objective Reward: Aqua Cabbage Roll

In order to trigger this Side Story you first need to complete the events of Water Seven. This includes heading into the Sewer, invading Enies Lobby, and, most importantly, defeating Rob Lucci. Once you've done all that all of the Side Stories of Water Seven will appear on the map, including My Treasure. You'll find the petitioner, a boy named Hien, in the northeast corner of Cafe Park.

Hien is distraught. One of the Yagara (the squatic seahorse animals that taxi people around) stole his Germa 66 dolls, and they're currently spread all over Water Seven. You'll need to look high and low to get the things back. The Germa 66 dolls are in the following locations, each held - or formerly held - by a Yagara:
  • The first Yagara is floating in the water right next to Hien, though the last rider took it away. You're looking for someone with a light blue outfit and glasses. Head west of Hien, down a pillar-filled alleyway in the northwest of Cafe Park, to find the guy. He'll hand over the Poison Pink Figure.
  • The second Yagara is floating in the southeast of Elevator - Top Floor, south of the Rental Bulls. It gave its doll to a family that's looking for jewels. It just so happens that there's a Money Exchange a short walk northwest of the dock that fits the bill. Speak to the little girl on the couch in here to receive the Stealth Black Figure.
  • The little girl will point you to Canal Restaurant, the area just north of Dock One on the east side of Water Seven City Area. Check the stairs leading to the water's edge on the west side of this area, more or less in front of the restaurant with tje green facade, and Luffy will pluck the Sparkling Red Figure out of the water.
  • The third Yagara, who had the fourth doll, is in the water a short walk west of where you found Sparkling Red. It mentions an old lady who sits near a fountain to the south of Canal Restaurant. You'll find the woman north of the entrance to Dock One, by the nearest fountain, and she'll give you the Winch Green Figure.
  • The final Yagara is down some steps to the south of the entrance to Dock One. It has the doll, but wants to trade for Sazae Kancho Pescatore. If you don't have one in your inventory you'll need to whip some up at a bar or tavern with Sazae Kancho Liver and Desert Tomatoes, both found in Alabasta. Bring the dish to the Yagara to receive the Shocking Blue Figure.

Take all five dolls back to Hien to resolve the quest. Seems like he cries whether he's happy or sad, which is fine.