As I don't know the exact story, I can't say for sure. But I assume the girl herself is a main character. There might also be characters like her family members, friends or antagonists who interact with her and are important to the story.
There could be the girl, of course. And perhaps there is a love interest in the story. If the girl can't help her feelings of love, then the person she loves would be a main character. There might also be a mentor - like an older person who gives her advice on how to deal with whatever it is she can't help doing.
Not having read the story, it's a mystery. However, in many stories with a girl as the central focus, there could be a sidekick - a best friend who is with her through her journey. And there might be an authority figure, like a teacher or a boss if it's set in a school or work - related environment, who has to deal with the girl's 'can't - help - it' situations.
Typically, there would be a male protagonist who is trying to pick up the girl. There might also be some friends or comrades that accompany him in the dungeon adventures.
The 'the girl can't help it story' could be a variety of things. It could be a story of a girl who is in a difficult situation and she can't help but make certain choices because of her circumstances. For instance, if she is in a poor family, she can't help but try to find ways to earn money at a young age. Or perhaps she has a condition that makes her act in a certain way and the story is about how she copes with it and how those around her react to her behavior.
Well, without more context, it's hard to say precisely. Maybe it's a story where the girl can't help but follow her heart in a particular situation, like falling in love despite obstacles. Or perhaps she has a habit or trait that she can't control and that causes various events to unfold in the story.
I'm not sure specifically which 'the girl can't help it story' you are referring to. It could be about a girl who has some sort of compulsion or irresistible urge that drives the plot of the story.
There are Skeeter, an aspiring writer. Then there are maids like Aibileen and Minny. Skeeter wants to write about the experiences of the black maids, and Aibileen and Minny are two of the maids who share their stories with her.
Since we have no details about 'the 100 girl story', we can only guess. Maybe there is a leader among the 100 girls who is a main character. Or there could be a few girls who are different from the rest in some way, like having unique skills or personalities, and they are the main characters.
Since I don't know the details of the 'fargo i can help story', I can't say for sure who the main characters are.
Since it's a light novel about a dungeon, the main characters could include a young and inexperienced adventurer as the central figure. There might be a female character who is not easy to meet in the dungeon as the title implies, but she could be important in some way, like having a key to a special part of the dungeon. And there could be some rival adventurers who add conflict to the story.