Some fanfics focus on the growth of their characters within the relationship. Jean might become more confident and decisive because of Mikasa's influence, while Mikasa could learn to open up more and show her softer side through her interactions with Jean. These character - driven themes are quite popular in Jean x Mikasa fanfic as they allow for a more in - depth exploration of their bond.
Often, survival is a theme. Given the nature of the original story they are from, fanfictions might show how Jean and Mikasa rely on each other to survive in difficult situations. Also, loyalty is a big theme. Their loyalty to their comrades and to each other can be a central focus, with stories exploring how far they would go to protect one another.
One common theme is the exploration of their relationship in a world full of danger. Since they are both in a harsh environment, their bond can be a source of comfort and strength.
One common theme is friendship. They are both strong female characters, and writers often explore how they could become friends or allies. Another theme is rivalry. Given their skills, they could be seen as rivals in some stories.
One common theme is the exploration of their different personalities. Jean might be more outgoing while Annie is more reserved, and how they bridge that gap.
Another theme could be adventure - based. Since they are both important characters in the Genshin Impact world, they often embark on adventures together in fanfics, which also helps to develop their relationship further. For example, they might go on a quest to save Mondstadt from a new threat and during that, their feelings for each other grow.
One common theme is friendship development. Writers often explore how Jean and Nico's relationship evolves from acquaintance to a deeper bond. Another theme could be adventure. They might be put in fictional scenarios where they go on adventures together and learn more about each other through those experiences.
One common theme could be friendship evolving into something more. The oc and Jean Gret might start as friends and then develop romantic feelings over time.
One common theme is the discovery of self. The OC often goes through a journey of self - discovery while interacting with Jean Grey. For example, they might learn about their own powers or their place in the world because of their relationship with her.
One major theme is the struggle between the OC's normal life and the extraordinary world of mutants that Jean Grey represents. Also, themes of acceptance are quite common. The OC may face discrimination, and Jean Grey helps them through it. For example, in some fanfics, the OC is a mutant with a very visible mutation, and Jean Grey uses her telepathy to help the OC accept themselves. It can be a very emotional and relatable theme. There are also fanfics that revolve around the theme of sacrifice, where either the OC or Jean Grey has to make a difficult choice to save the other or the entire mutant community.
You can try some popular fanfic websites like Archive of Our Own (AO3). There are a large number of fanfics about different pairings, including Jean x Mikasa. Just use the search function on the site and type in 'Jean x Mikasa' to find relevant stories.