In The Legend of Zelda: Skyward Sword HD, Link will not only have to fight all sorts of dangerous enemies to save the world, but also help common people solve their problems. Completing these side quests isn’t mandatory to complete the story, but clearing them will allow you to obtain some very nice rewards that will make your life easier in the main campaign.
Here’s how to complete the Missing Child sidequest.
How to Complete the Missing Child Sidequest in The Legend of Zelda: Skyward Sword HD
The Missing Child Sidequest becomes available right after placing the Ruby Tablet inside the Statue of the Goddess. After doing this, go outside to find Wyrna. Talk with her to learn that she is looking for her daughter and needs help.
After this is done, you can get a little more information on the situation by talking with Orielle and Rusta. Apparently, monsters are kidnapping children, and one in particular has been spotted near the graveyard in Skyloft.
When you are ready to complete the quest, get back to your room and sleep until night. After this is done, head over to the graveyard located southeast of Skyloft and hit the tombstone near the tree. Push it to unlock the nearby shed. Enter the building and then go down the ladder: at some point, you will encounter the Demon Batreaux, who will reveal the truth to you after you have swung your sword at him.
After befriending Betreaux, you are pretty much done. Sleep until morning, speak with Wyrna again, and you will receive 5 Gratitude Crystals for your trouble.