Throughout the game you will notice conversational options to flirt with the Peatrice, the Item Check girl. After flirting with her head to her house located directly below the Bazaar and sleep until night. When you wake up, speak with her father Peater who is sitting at the table. He will inform you of his feelings about his daughter’s dating habits and will begin the Item Check Crush side quest.
To complete the quest simply flirt with Peatrice again during the day and speak with her another night. You then have the option to either convince her that you share her feelings to receive 5 Gratitude Crystals or you can break things off with her and receive 5 Gratitude Crystals from her father.
Note: this quest can only be started after a certain point in the game even though you can flirt with Peatrice very early on, and can only be completed after Link heals the Water Dragon.Skyward Sword - Side Quest: Item Check Crush,