Knights Are Brave and Strong

Before she can become queen, Princess Shelby has to go on a quest.
Before she can become a knight, Katherine has to do the same.
The two have been best friends since...forever. So when Shelby's father, the King, has the bright idea of sending them on the same quest to deliver a message to Queen Lizzie, Shelby's sister who rules a neighboring land, as both of their quests, nobody objects.
And now the two have to travel halfway around the world together, proving just how brave, strong, and smart they are.