This kind of fanfiction could potentially explore Hermione's curiosity or it might be used to develop a complex plot around her character's exploration of different aspects of sexuality. But it really depends on the specific story and the author's imagination.
The first appearance of lesbian porn stories online is difficult to determine precisely. It likely occurred gradually as the internet grew and different types of content became available, without a clear-cut beginning.
One popular lesbian supernatural romance novel is 'Ash'. It weaves a story of a female protagonist's encounter with a mysterious and alluring female figure in a world filled with magic and secrets. The relationship between the two characters is both tender and filled with the tension that comes from the supernatural elements in the story.
Another characteristic is the exploration of female - female relationships in a way that is unique to the genre. It often involves themes of acceptance, not just from society in the fictional world but also within themselves. The characters may have to overcome personal biases or past traumas related to their sexual orientation while also dealing with the supernatural threats or mysteries in the story. For instance, in a story where a lesbian couple is trying to solve a mystery involving a haunted house, they also have to face their own relationship insecurities.
The main distinction of porn with a story genre from regular porn is the presence of a coherent narrative. Regular porn often jumps straight to the sexual action, while the story genre tries to add some kind of story framework around it. But in the end, both are adult-oriented and feature explicit sexual content.