Once the second Skytree has been restored, the next morning you'll bump into Elise outside of your house. She and her dad had set out on a journey to buy supplies for the inn because nothing would grow in the barren land. Now that they have returned, she is surprised to see water flowing once again. Go visit the inn to meet the head chef, Bastian. You notice an unused fishing rod sitting on a dresser. Elise says it was hers, but she is going to give it to you as a gift. Bastian will request that you bring him 3 Perch.
You can catch these fish in the stream that runs down from the Harvest Goddess Spring. Just walk up to the water and you'll see a prompt to press your A Button to start fishing. Once your line is in the water, you just have to wait until you see a ! appear above your head. At that point press the A Button over and over until you reel in the fish.
Bring the 3 Perch (not Yellow Perch) back to the inn and a cut scene will automatically trigger. Bastian wants to put on a fish dinner party, but the kitchen isn't large enough. Elise will meet you at your house to borrow your kitchen; she'll give you the recipe for Grilled Fish and teach you how to cook.
To use the kitchen, press the A Button when standing next to it. Elise and Bastian already gave you the Salt you need for making the Grilled Perch. You'll find the recipe under the 1-star category of recipes. Make 3 Grilled Perch using your kitchen and then walk back to the inn to hand it over to Bastian. The chef will be pleased with your help. All of the existing villagers will gather to have a fish party with your Grilled Perch. After the party is over, the restaurant Auberge Bastian will be available Mondays through Saturdays from 10:00 am to 8:00 pm.
The gathering and cheer from all of the villagers at the fish party has restored additional power of caring. Rowan instructs you to return to the Harvest Goddess Spring, where she will revive the third Skytree and bring back the Harvest Sprite of water, Dewey. You now have more area to explore.