Genshin Impact 2.1 - Granny Komaki Hidden Quest Achievement with 3 Chest Rewards
Location : Bourou Village, Watatsumi Island, Inazuma
This hidden quest achievement is the final day / day 5 quest from Granny Komaki
so you should talk to her and finish the quest for 4 days IRL time.
note : clear the puzzle inside Suigetsu Pool area first before do this quest