There are several themes that are quite popular. One is the idea of redemption. Since Rin has the demon blood in him, some fanfics might explore how Shura could be involved in his journey towards redemption, or how their relationship is affected by Rin's struggle with his demon side. Another theme is the clash of cultures. Rin grew up in a different environment compared to Shura, and this can lead to interesting scenarios in fanfics where they have to bridge the gap between their different ways of thinking and living. And then there's the theme of secrecy. Their relationship might need to be kept a secret for various reasons in the 'Blue Exorcist' universe, and fanfics often play with this concept, creating a sense of mystery and tension in the story.
The theme of Rin's training as an exorcist is quite common. Fans like to write about how he learns new skills, masters his powers, and becomes a better exorcist. It could be about a particular difficult training session he has to go through, or how he discovers new ways to use his abilities in the fight against demons.
The world of Blue Exorcist itself provides a rich backdrop for Rin x Shura fanfiction. The setting of the True Cross Academy, the existence of demons and exorcists, all add layers to their relationship. Writers can create stories where Rin and Shura have to face demons together, or where their relationship is complicated by the rules and politics of the exorcist world. This combination of interesting characters and a detailed world makes for great fanfiction.
Some Blue Exorcist fan communities on Reddit could be a source as well. There are subreddits dedicated to the series where fans might share their own fanfictions or recommend ones they've read. You can post a request specifically asking for Rin x Shura fanfictions. However, make sure to follow the subreddit rules when interacting with the community.
Some fanfics focus on Rin's power development in a different way from the original story. Maybe she discovers new powers or has to learn to control her existing ones in a more challenging situation. There are also fanfics that explore Rin's family relationships in more depth, especially her connection to her father. This could involve flashbacks or new revelations about her family's past.
In 'Blue Exorcist Rin fanfic', a very frequent theme is Rin's battle against his inner demons, both literally and figuratively. His journey to master his demonic powers while still remaining true to his human side is often explored. Also, his relationship with the exorcist community, whether it's facing discrimination or finding acceptance among them, is a common theme. Additionally, his friendships, especially with the people he meets at True Cross Academy, are often a big part of the stories.
One common theme is innocence. Since it's about 'baby Rin', it often shows his pure and naive side before he fully understands the weight of his demon heritage. Another theme is friendship. It might explore how Rin forms his first friendships at the academy.
You can try searching on fanfiction platforms like Archive of Our Own (AO3). There are often a great number of fanfics about different pairings from 'Blue Exorcist', including Rin x Shura. Another option is FanFiction.net, though the quality may vary more there. You can also check out some Blue Exorcist - related forums or communities where fans might share their favorite fanfics or even write some themselves.
Fanfiction.net is also a great place to search. There are many dedicated fans who post their Blue Exorcist fanfics there. Just be sure to use the search bar and type in 'Amaimon x Rin' to find relevant stories. However, the quality can vary, so you might need to skim through a few to find the really good ones.
One theme that pops up a lot is the struggle with their exorcist duties while also dealing with their feelings for each other. They have to fight demons and protect the world, but at the same time, they are developing these complex emotions. It's like a balance between their personal lives and their responsibilities. And also, the theme of acceptance is there. They have to accept each other's flaws and strengths as they get closer.
Love and friendship are also big themes. The relationship between Rin and the OC can range from a slow - burning friendship that turns into love, to an instant attraction. In many stories, they support each other through difficult times, like when facing powerful demons or dealing with the politics within the exorcist community.