Pokemon Sword and Pokemon Shield have a number of side quests that often reward you with special pokémon items. One such quest is the delivery of a love letter from Hammerlock to Ballonlea.
How do I get an old letter from Paula?
To start a mission, you need to get an old love letter. You can buy it in Hammerlock (you will find yourself here after the third gym). Get to the old castle, which is located up the stairs on the east side of the city, and talk to a little girl named Paula. Paula wants you to give an old letter to a boy named Frank. You can find it in Ballonlea.
Where can I find Frank in Ballonlea?
The town of Ballonlea is located through the Gilmwood Club, which is accessible after the fourth hall. In Ballonlea, go to the stadium and enter the first house to your left. Inside this house, there is an old man. Talk to him to find out that he is Frank. In short, Frank liked Paula when they were both kids. Give him the letter, and in return, you will get you the Scarf of Choice. It increases the speed of the Pokémon, but it can only be used with one move.