With You

Where: Start by teleporting to the southern Byakko Plain waypoint.
What: You'll need to head west across the water to reach Amakane Island.
What to do: Just make your way over there. As you approach the stone path leading onto the island, a scene will trigger. Paimon will be super excited, but then a little bummed to find out the festival is pretty much over. Ayaka explains it's the last day, so most people have already headed home. More for us, right?

Where: You're on Amakane Island, near the festival entrance.
What: After the scene, follow Ayaka up the trail. She'll stop at a vendor named Sanden.
What to do: Approach Sanden. Another scene will play. Ayaka will mention the festival isn't quite closed yet and you should see what you can. Sanden recognizes Ayaka and offers you both a free mask. Ayaka, being Ayaka, doesn't want any special treatment or charity; she just wants to enjoy the festival like anyone else. She'll tell you she brought you along because she genuinely wanted to spend time with you, not just for sightseeing.

Where: Continue following Ayaka up the trail.
What: She'll stop by Shimizu, the Fortune Slip Vendor.
What to do: Go over and talk to Shimizu. You'll get another scene. Shimizu also offers Ayaka something for free, mentioning his uncle was helped by the Yanshiro Commission. Ayaka turns it down again, but after asking your opinion, she agrees to take a fortune slip for free. Draw a slip for yourself, Paimon, and Ayaka. It turns out you, Paimon, and Ayaka all get the same fortune, which Shimizu explains means you're all in for a good streak of luck!

Where: Follow Ayaka further up the trail.
What: She'll stop at a food stall selling Inazuman specialties on your right.
What to do: Ayaka tells you to pick whatever you want, her treat! Paimon, naturally, picks a bit of everything. You'll get to try some of the food, and you all seem to really enjoy the Sakura Mochi. Ayaka asks the owner, Murakami, how it's made. He's happy to share the recipe, mentioning he's returning a favor since you gave the recipe for Pizza to Kiminami Restaurant. Murakami then gifts you the recipe, so you'll receive the Recipe: Sakura Mochi.

Where: Keep following Ayaka.
What: You'll reach Yoshikawa, the Prayer Plaque vendor.
What to do: Another scene plays. Ayaka explains what prayer plaques are, and Paimon notes it's similar to releasing lanterns during the Lantern Rite in Liyue. You all make a wish and hang your plaque on the rack. Your wish is to see your sibling again, while Ayaka wishes for peace in Inazuma and good health for her loved ones.

Where: You're finishing up at the festival.
What: Ayaka mentions she's run out of time and the festival is winding down.
What to do: You'll return to Chinju Forest with her. She shares some final thoughts, expressing how happy the day made her. Then, she has one last surprise: a song and dance performance! After that, you all chat about how much you enjoyed the day, and the quest concludes.