Such a manga might have elements of family pressure, cultural expectations, and the girl's inner struggle. There could also be potential love interests or allies who help her.
One reason could be for the sake of exploring different relationship dynamics. Fans want to see how Harry would react in a situation that is completely out of his control, like a forced marriage. It adds a new layer of drama to his character.
It could be someone from a rival village. Maybe as part of a peace treaty, Naruto is forced to marry a kunoichi from a village that was once at war with Konoha. This would create a lot of tension and interesting storylines as Naruto has to deal with the cultural differences and the past hostilities between the two villages.
A powerful and ancient magical being might force Harry to marry. This being could have its own motives that are not immediately clear. It could be related to some prophecy or an old magical law that only this being knows about. Harry would then have to figure out the nature of this being and how to persuade it to release him from the forced marriage.
"The Prince of Time Traversal Is Too Impatient." This was an ancient romance novel about a 26-year-old mature woman who transmigrated into a 13-year-old girl, and her life became a tragedy. She was the heir of the 108th generation of the Heiye family. Her medical skills and poison techniques were a piece of cake, and she was even better at disguising herself with martial arts. However, the emperor had decreed that she should be happy, and she had to face the harassment of the sick prince. As a fake wife, she still had to help her husband deal with all kinds of troublesome matters. In the end, the sunny and beautiful man and the golden-masked man suddenly appeared.
I'm not sure specifically which 'Forced to Marry the Billionaire' story you mean. There could be many novels or tales with such a title. Generally, in such a story, it might involve a situation where the protagonist is compelled to marry a billionaire perhaps due to family debts, business arrangements, or some kind of blackmail. Without more context, it's hard to tell the exact full story.
One common theme is the struggle for acceptance. The human character usually has to accept the fact that they are married to a dragon, which is a very different being. For example, in many stories, the human initially resists but then learns to see the dragon as more than just a fearsome creature.
Perhaps it's a creative way of saying that a person is so immersed in the world of romance novels that it's like they're being forced into it. For example, if all their friends are into it and keep pushing them to read more, they might feel forced to marry the idea of constantly reading romance novels.
If it's in an academic setting, try to find the aspects that interest you the most in the romance novels. Focus on the historical context, character development or the language used.
One popular 'Harry forced to marry' fanfiction might be 'Forced Bond' where the author creates an interesting plot around the forced marriage concept. It delves into how Harry copes with the situation and the relationships that develop as a result.