Scattered throughout The Legend of Zelda: Skyward Sword HD are a number of side quests that players can complete to earn Gratitude Crystals. These special gemstones are feelings of gratitude in crystallized form and can be traded with the friendly monster Batreaux for a number of rare and useful items once enough have been acquired.
Before players can begin tackling any side quests, however, they'll first need to complete the Skyview Temple dungeon and then place the Ruby Tablet into the altar inside the Chamber of the Sword on Skyloft. Once that's been taken care of, the first side quest will be unlocked and can now be completed at any time the player chooses.
How To Start The Lost Child Side Quest
After leaving the Chamber of the Sword and making their way through the small stone courtyard, players will run into a woman named Wryna who is worried about her missing daughter, Kukiel. She'll ask Link to help find her and mention that Kukiel was last seen being carried off by a monster with a scary face. Players should agree to help and then make their way over towards the graveyard in the southeastern part of Skyloft.
How To Find Kukiel
Shortly before arriving at the graveyard, players will run into a brown-haired woman named Orielle. She's strolling around in an open area near some houses and has an orange bubble floating above her head, which makes her fairly difficult to miss. Upon speaking to her, players will learn that an old man over at the Lumpy Pumpkin regularly rants about hidden monsters in Skyloft, so players should jump off the nearest ledge and summon their Loftwing by hitting down on the D-pad.
The Lumpy Pumpkin is on a small island called Pumpkin Landing to the southeast of Skyloft. Unlike Skyloft where players can use the right trigger to dismount, here, they'll instead need to hit down on the d-pad while flying above the island. The Lumpy Pumpkin is the only building on the island, so after dismounting their Loftwing, players should head inside and look for Rusta; the old man sat around the large circular table. He'll tell Link that while taking a walk near the Skyloft graveyard in the middle of the night, he saw a monster hit the gravestone closest to the tree and then push it to open up a secret entrance. Naturally, this means returning to Skyloft.
Before doing so, however, those visiting the Lumpy Pumpkin for the first time should head upstairs and roll into the wooden support pillar a few times so that the chandelier drops. Not only will this allow them to pick up a Piece of Heart and some rupees, but it will also start the tavern owner's questline. Players should talk to Pumm to get the Hot Pumpkin Soup and then deliver it to Eagus in the Knight Academy Sparring Hall on Skyloft.
With all of that taken care of, players should now head to one of the rooms in the Knight Academy or any villager's house and find themselves a bed to sleep in. As the monster has only ever been seen in hours of darkness, Link will need to sleep until nighttime before heading over to the graveyard. As per Rusta's ramblings, players will need to roll into the gravestone closest to the tree by dashing using B and then pressing in the left analog stick. Upon doing so, a rune on the gravestone will begin to glow and players will be able to grab and push the stone by holding A and pushing up on their left analog stick.
Once the stone has been moved, a short cutscene will play revealing the entrance to a nearby structure, so players should head straight there and climb down the ladder. As they make their way down some wooden planks towards a house, they'll hear a loud scream and, upon heading inside, will find Kukiel standing next to a terrifying monster. As soon as Link pulls out his sword, however, the monster will cower in terror and explain that he's called Batreaux, is a friendly monster, and has no intention of harming Kukiel or Link.
Claiming The Reward
Kukiel will tell Link that she'll return home in the morning and ask him to pass on the message to her mother. There's no need to actually do this though. Instead, players should find somewhere to sleep until morning and then head on over to Kukiel's house. Thankfully, it's marked on the map, and can be easily located just to the east of Skyloft's central Bazaar. When Link heads inside, Batreaux will thank him for finding her daughter before handing over five Gratitude Crystals as a reward.
When Link first encounters Batreaux, the monster mentions that he needs Gratitude Crystals in order to take human form, so with their Gratitude Crystals in hand, players should now return to Batreaux by taking the ladder over by the graveyard and following the path down to his house. If players talk with him, he'll reward them with the Medium Wallet, which allows Link to carry up to 500 Rupees rather than the 300 that can be stored in his default Small Wallet.