You talk to Tansui about paying your tithe, but while negotiations are underway, a Confederate arrives asking for help.
This quest is available if you have completed the quest Open Water.
Starting the Quest
Talk to Tansui in the Ruby Sea to begin the quest. There will be a cutscene.
Search for Tansui
Go northwest to the stairs, and go down them. Then continue northwest to where the orange arrow is pointing in the map. Go to the southeast edge of the orange circle on the map and check on the sparkling Destination. There will be a cutscene.
Speak with Gosetsu
Talk to Gosetsu to proceed.
Search for Soroban
Go southeast to where the orange arrow is pointing in the minimap. Go to the northwest edge of the orange circle and talk to Soroban to complete the quest.
Aether Current Quest
With the completion of this quest, you can now start the blue quest "The Price of Betrayal" 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, talk to Soroban to accept the next quest: To Bend with the Wind.