One common theme is the struggle between good and evil. Jane is often portrayed as more of the 'good' side trying to stop Jeff who is seen as the 'evil' one. So there's a constant battle of morals.
Another theme is redemption. Sometimes in fanfictions, Jeff is given a chance to redeem himself through his interactions with Jane. It shows that even a character like him can have a change of heart. Also, love or at least an attraction can be a theme. Even though they are enemies, there can be a sense of underlying attraction that develops between them over time which makes for an interesting dynamic.
The theme of identity is also prevalent. Both Jeff and Jane have their own identities that are often explored in fanfiction. For example, how Jeff became the killer he is and how Jane is trying to define herself in relation to Jeff. These themes add depth to the stories and make them more than just simple horror - themed tales about two killers.
One common theme is redemption. Given their dark and violent pasts, many fanfictions explore the idea of either Jeff or Jane seeking redemption through their relationship. Another theme is the power of love to change, as they are two very damaged individuals and love might be the thing that can transform them.
Love - hate relationship is also very common. They are enemies by nature but in some fanfics, there's an underlying attraction or connection that they can't deny. This creates a lot of drama and tension in the stories.
One common theme is the battle between good and evil within their relationship. Since Jeff is a killer and Jane is often portrayed as more of an anti - hero or hero figure, their interactions can be seen as a struggle between these two forces.
One common theme is obsession. Nina is often depicted as being obsessed with Jeff, and this plays a big role in their relationship dynamics within the fanfics. Another theme is the idea of two 'broken' characters finding some sort of connection. Since they are both killers, they have a shared darkness that can either pull them together or tear them apart.
One common theme is fear. Since Jeff the killer is a horror character, the fanfictions often play on the reader's fear of him. Another theme is the idea of an unlikely connection. For example, the reader might be drawn to Jeff's dark side in some way.
One common theme could be the exploration of their dark and twisted natures. Since both characters are from the horror genre, their fanfictions might focus on their evil deeds and how they interact in a world full of chaos.
One common theme is the exploration of the 'forbidden' or 'taboo' relationship. Since Jeff is a killer, a relationship with an OC is not something that would be considered normal or acceptable in mainstream society. Another theme is the idea of redemption. As mentioned before, the OC might be the catalyst for Jeff to change his ways. Fear and danger are also prevalent themes. The OC is constantly in a state of fear due to Jeff's nature, but at the same time, there is an allure because of his mystery and power.
One common theme is the power struggle. Since both Jeff and Nina are killers, there can be a battle for dominance in the fanfic. Also, the theme of unrequited love sometimes pops up, with Nina loving Jeff but not always getting the same in return. And of course, the general horror theme of blood and gore is often there as it's part of their nature as killers.
The main characters are, of course, Jane the Killer and Jeff the Killer. Jane is often depicted as a vengeful figure, while Jeff is a well - known and terrifying killer. Their interactions are the focus of this fanfic.
One interesting plot could be their unexpected alliance. Maybe they are forced to team up against a greater evil in the fanfic. This would create a lot of tension as they have their own issues with each other but have to put them aside for the common good.