The side quest A GOOD LISTENER can be triggered when talking to CANDLIE. CANDLIE is found sitting next to a tea set at the far right of the second spider puzzle in PYREFLY FOREST. When the quest is activated, she will ask you to find their missing stuffed bear.
The stuffed bear is located in SWEETHEART'S CASTLE, underneath her statue in the courtyard. The stuffed bear will appear upside down and when interacted with will put you into a battle with a RARE BEAR. When the enemy is defeated, you will obtain the stuffed bear. You can return the bear to CANDLIE and complete the side quest.
Returning to CANDLIE and interacting with her leads to a cutscene where she finally reunites with her TEDDY BEAR. She then will grant the party the RUBBER DUCKcharm, which increases the user's DEFENSE by seven points. Afterwards, CANDLIE will resume her tea party with the TEDDY BEAR, signifying the completion of her sidequest.