You tell Soroban of your situation and he recommends that you to present your case to the village leader, Bunchin.
This quest is available if you have completed the quest Under the Sea.
Starting the Quest
Talk to Soroban in Tamamizu in the Ruby Sea to begin the quest.
Speak with Bunchin
Go west and attune to the Tamamizu Aetheryte, then go to the quest icon on the map and talk to Bunchin. There will be a cutscene.
Speak with Soroban
Talk to Soroban to proceed.
Slay an Unkiu
Go east up the slope and up through the cavern. When you find a fountain of water, stand on it to be launched up to the exit of the cave. The locations of Unkiu will be marked on the minimap. Slay them until you get a carapace.
Deliver the Unkiu Carapace
Go northwest into the cave, go left down the slope, go into the tunnel at the end, and go to where the orange arrow is pointing in the minimap. Talk to Soroban to hand over the Unkiu Carapace and complete the quest. There will be a cutscene.
Aether Current Quest
With the completion of this quest, you can now start the blue quest "The Sword in the Stone" in the Ruby Sea. Completing that quest will attune you to an Aether Current in this area.
Next Main Scenario Quest
After you complete the quest, you will need to be at least level 63 to proceed to the next quest. After you reach level 63, talk to Soroban to accept the next quest: In Soroban We Trust.