During your exploration in southern part of Dragonspine, you might stumbleupon item called Drifting Bottle. When you interract with the item, monologe contained inside the bottle will appear.
There’s 3 Drifting Bottle in Dragonspine and back then no one know what is this item used for. Turned out this item is requirement to unlock world quest in Inazuma: Hiromi’s Watch.
Here’s locations of all Drifting Bottles in Dragonspine, with detailed screenshot below:
Drifting Bottle #1
Drifting Bottle #2
Drifted on the small islet.
Drifting Bottle #3
Near Ruin Grader. You need to defeat this Ruin Grader before interracting with this bottle.
After obtaining all Drifting Bottle, you will get new item called Someone Drifting Bottle which is required for Hiromi’s Watch quest and 30 primogems as reward.