Once back in Skyloft, talk to the little boy on the plaza to the south. Look for Beedle's flying shop in the sky and launch your Beetle to bump into the bell and stop the shop. Get close and grab the rope to climb aboard. Beedle is selling all kind of items, especially the Bug Net the little boy is so interested in. Look at this item and buy it for 50 rupees. Get out, jump down and go back to the Bazaar. Speak to the Gear Shop's blacksmith and buy the Iron Shield for 100 rupees.
Head back into the Goddess Statue, all the way to the north and place the Ruby Tablet into its location. A second red column will appear northeast of the island. As you leave, you will meet Kukiel's mother who his looking for her little girl. Be careful! If it's nighttime, you will have to come back to this place during daytime to meet her. Agree to help her, then go down the two sets of stairs and go left. Talk again to the little boy who is thinking about the graveyard. Cross the bridge to the east which leads to the residential district, then go right and talk to the braided young girl. She says that an old man is telling everyone that a monster lives there. This man is at the Lumpy Pumkin, located on an island east of here. Go to a diving platform, dash and call for your Loftwing. Fly towards southeast, where you can see a purple symbol. Fall down when you are over it.
Take a look at the statue, then enter the Lumpy Pumpkin. Talk to the waitress, the barman selling the pumpkin soup, and the old man. Ask him for more information so he tells you that at night, in the graveyard, he saw a monster hitting a gravestone near the tree, then pushing it. Get out and head east. Open the chest to find an extra Adventure Pouch so you can carry one more item! Leave the island and get back to Skyloft.
You now have to wait for night to come. Enter a house and get close to the bed. Choose to sleep until the night comes! Then leave the house and head to the graveyard located east of the island, beyond the residential district. As the old man said, hit the stone next to the tree, then move it: the storage shed's door opens! Get in and go down the big ladder. Walk on the planks, you will hear a scream! Get in the hut, then attack the monster... which isn't a real monster :-) This nice demon called Batreaux tells you about Gratitude Crystals which appear when a human is happy. Agree to help him gathering these crystals so he can turn into a human, and he will grant you the ability to see these crystals. Talk to little Kukiel, then get out and go back to the graveyard. Get into a house and sleep until dawn. Get out, cross the bridge and get in the house to the right, at Kukiel's. Speak to her mother, which allows you to receive five Gratitude Crystals! Go back to Batreaux and give him the crystals, he will thank you with the Medium Wallet!
Now head south of Skyloft on the plaza and talk to the worried man. Ask him about his concerns so he tells you about his sister who still hasn't come back from her walk to a newly-appeared colourful island to the southwest. You can either choose to go looking for the young lady now or later...