Delaroche is a lady primarily known for her passion for professional fishing. Enthusiasts of the Inazuman activity (remember the highly hyped "Fishing for Jade" from 2.x) have already experienced the pros and cons of Fontaine fishing with every fiber of their being - thanks to the purchase of the "Fleuve Cendre ferryman," the guide for which is available here. So, she's been acquainted with for a long time. But apart from the commercial side of her personality, she can offer a hidden three-day quest with a decent number of rewards. That's what we'll talk about next. 

How to Get the Secret Quest with Delaroche in Genshin Impact

Head to the Fishing Guild base (which is basically just Delaroche herself). Fish nearby - the local catch is obtained with Sugar Bait, Sour Bait, and Repair Kit - and after catching your first fish, initiate a conversation as you exit the fishing menu. This will begin the first day of the quest. 

Hidden Quest with Delaroche: Day One

Your task is to dive and genuinely inspect the hook, and with the appropriate conclusions, attach a fish to it (any fish will do). The location is marked in yellow and is located right under the improvised pier.

The screenshot covers the first and second days at once since it shows the same item. Then congratulate Delaroche on your - fictional - catch. As a result, she'll reward you with 20 Primogems and 150 Adventure EXP. 

Hidden Quest with Delaroche: Day Two

After one real day (on the day following the previous one), approach the girl again with a conversation. The algorithm is equivalent to the previous one, only this time you should attach bait (any bait will do) instead of a fish. The reward is 150 Adventure EXP, 20 Primogems, and 25,000 Mora as a bonus. 

Hidden Quest with Delaroche: Day Three

This time, after the dialogue, you simply need to retrieve an item from the bottom - bait, which is dangerous because it attracts monsters due to its negative property - and then hand it over to Delaroche.

Then calmly walk away with 150 Adventure EXP, 20 Primogems, and 25,000 Mora. Good luck! Credits for the last two screenshots go to NJMH Gaming.