Fishing Guild Member O'Fulle asks you to find a missing box. Its owner dropped it near the water. Keep an eye out for it while you're fishing. If you find it, feel free to open it up so that you'll know who to return it to. This is an one-time quest.
O'Fulle asks you to find a yellow treasure chest. Its owner lost it in the water. If your fishing skill is at least level 12, try using a special bait to find it, or, you could ask around to see if anyone has already found it.
Kiki's Letter
Target: Kiki
You find a letter when you open the yellow chest. Take it to Mineral Trader Kiki at the Blacksmith Shop in the village.
Searching For a Strange Box
Target: O'Fulle
O'Fulle asks you to find a yellow treasure chest. Its owner lost it in the water. If your fishing skill is at least level 12, try using a special bait to find it, or, you could ask around to see if anyone has already found it.
Delivering Kiki's Letter
Target: Kiki
You find a letter when you open the yellow chest. Take it to Mineral Trader Kiki at the Blacksmith Shop in the village.
Go fishing. Use the quest items Icy Air Fishing Lure as bait. Every bait should catch a chest. Fish until you get Big Yellow Treasure Chest. The quest bait may not be enough to catch this particular chest, so you can use ordinary bait afterwards.
Then return to O'Fulle and give him Big Yellow Treasure Chest. In return he will give you Kiki's Letter.
Take the letter to Mineral TraderKiki at the Blacksmith Shop in Town of Giran. The quest is complete; the reward is Elven Ring.
in Town of Giran 
will ask you to bring him 
Big Yellow Treasure Chest. He'll also say that your fishing expertise must be level 12-14. 
Icy Air Fishing Lure as bait. Every bait should catch a chest. Fish until you get Big Yellow Treasure Chest. The quest bait may not be enough to catch this particular chest, so you can use ordinary bait afterwards. 
Kiki's Letter. 
Elven Ring. 
