Perhaps he likes fanfiction that shows Hermione in romantic relationships. It could be pairings that are not the most common in the fandom, and the new dynamics in those relationships intrigue him.
He could be into the ones that focus on Hermione's academic achievements. Maybe stories where she discovers new spells or makes great contributions to the wizarding world's knowledge.
It's possible that he's fascinated by fanfiction that places Hermione in dangerous or challenging situations. For instance, she might be in a situation where she has to use her wits and magic to escape from a powerful dark wizard. These types of stories can be really exciting and show Hermione's strength and resourcefulness in different ways compared to the original books.
Maybe he's attracted to the unique interpretations of Hermione's character in the fanfiction. Different fanfictions might show different sides of her, like her intelligence in new and exciting ways.
One common theme is the idea of redemption. Often, Rowle is depicted as a character in need of redemption, and Hermione plays a role in that process. For example, she might help him see the error of his ways.
Well, Snape has a mysterious past and his relationship with the main characters, especially Harry and his mother Lily, is full of depth. Fanfiction often delves deeper into these aspects. Hermione, with her love for knowledge and understanding, would find these explorations in Snape fanfiction fascinating. It allows her to see Snape from different angles that the original books might not have fully explored.
Maybe Rowle is under the orders of a more powerful dark wizard. In the world of Harry Potter, there are always those higher - ups in the dark side who might want Hermione for her knowledge of magic, especially things like ancient spells and magic theory. So Rowle could be tasked with kidnapping her for that purpose.
Perhaps the fanfiction focuses on Hermione's research into some dark magic spells and she finds out that Rowle has some knowledge about them. So, she has to get close to him to learn more. In the process, they might develop an unlikely friendship. Rowle could start to see the value in the light side of magic through Hermione's influence.
Another plotline could involve Hermione trying to redeem Rowle. She could see some good in him despite his actions and attempt to turn him away from the dark side. This might include showing him the positive aspects of the wizarding world that don't involve dark magic.
Another theme could be redemption. If Rowle is portrayed as a character who has done bad things in the past, falling in love with Hermione could be a path towards redemption for him. The love story could be intertwined with his journey to become a better person. Also, there could be themes of secrecy and forbidden love, as their relationship would likely be frowned upon by many in the wizarding world.
Redemption is a big theme. Since Thorfinn has ties to the dark side in the original story, many fanfictions explore the idea of him being redeemed through his interactions with Hermione. Also, the theme of unexpected alliances can be found, as they come from different 'worlds' within the wizarding universe.
There are probably some Thorfinn Rowle and Hermione romance fanfictions, but they may be hard to find. Since Thorfinn Rowle is a relatively minor character in the original series, not many authors might be inspired to write about this pairing. But if you search specifically for it on major fanfic platforms, you might get lucky.
Rowle is another main character. He's usually a dark wizard, so in this fanfiction, he could be a complex character with his own motives and backstory that Hermione has to deal with.