There could be family members of the stolen girl as main characters. For example, her parents. They would be the ones most affected by her being stolen and would probably be the ones trying to find her. So, they could play a major role in the story. Also, there might be a detective or someone in a position of authority who is trying to solve the case of the stolen girl.
The stolen girl is likely to be one of the main characters. She is at the center of the story with the title. And perhaps the person who stole her could also be a main character as their actions drive the whole plot.
Maybe there are other characters in the 'other stories' part who are main characters in their respective tales. It could be a lonely traveler who has his own story of struggle and discovery. Or a young artist who is facing some sort of challenge in a big city. Each of these characters in the different stories could be considered main characters in their own right within the collection.