One common theme is friendship. Despite their different personalities and roles in the Kingdom Hearts universe, fanfictions often explore how they could become friends or allies. For example, they might overcome their initial differences and work towards a common goal.
There are also fanfictions that explore the idea of redemption. Maybe Marluxia or Axel has done something wrong in the context of the game's story, and the other character helps them find a path to redemption. This can add an interesting layer of depth to their relationship.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, including Kingdom Hearts. Just use the search function and type in 'Kh Marluxia X Axel' to find relevant stories.
One common theme is their relationship within the Organization XIII. Writers often explore how their different personalities interact, like Marluxia's more devious nature compared to Vexen's scientific and somewhat cold demeanor. Another theme could be their loyalty (or lack thereof) to the Organization. Some fanfics might also focus on a possible romantic or platonic bond that forms between them as they work together on various missions in the Kingdom Hearts universe.
One common theme is friendship turned into something more. Since they start as friends in the Kingdom Hearts series, many fanfictions explore how their relationship deepens into a romantic one. Another theme is the struggle with their identities. Both characters have complex backstories related to their identities, and this can play a big part in the fanfictions as they navigate their relationship.
One common theme is adventure. Axel and the reader might go on some exciting quests together in the fictional world. Another is romance, of course, with all the sweet and sometimes angsty moments between them.
Love, of course, is a very prevalent theme. Whether it's a slow - burn romance or a sudden realization of feelings, it's often at the center of the stories. And sometimes there's the theme of redemption, where one of them has made mistakes in the past and the other helps them become a better person.
One common theme is the fragility of their relationship, just like dolls can be fragile. Their connection is often shown as something that needs to be carefully nurtured.
One common theme is the exploration of a passionate relationship between Axel and the reader. There's often a focus on the emotional connection that leads to more intimate moments. Another theme can be the idea of Axel protecting the reader, which then transitions into a romantic and physical relationship.
One common theme is redemption. Riku has had his own journey of redemption in the Kingdom Hearts series, and in fanfiction with Namine, it could be about him finding further redemption through his relationship with her. Another is discovery, as they discover new sides of each other.
One common theme is the redemption arc. Axel might be a character who has done some not - so - great things in his story, and in the fanfic, the Reader can be the catalyst for his change and redemption.
One common theme is friendship. Many fanfics explore how their initial friendship develops into something deeper. For example, they might start as comrades in a difficult situation and gradually realize their feelings for each other.