Another plot could involve Tamaki getting injured during a fight. Shinra then takes it upon himself to take care of her. As he nurses her back to health, they have a lot of time to talk and get to know each other on a more personal level. This could lead to them realizing that they have a lot more in common than they initially thought, and their relationship could grow from there.
In a fanfic, their relationship could also develop through moments of vulnerability. Let's say Shinra has a nightmare about his past and Tamaki is there to comfort him. Or Tamaki has a moment of self - doubt about her abilities, and Shinra gives her an encouraging speech. These moments of showing their true selves and being there for each other can deepen their connection. It's about creating situations where they can be honest with each other and build an emotional bond.
A sense of loyalty is often a theme. In these fanfics, Shinra and Tamaki are shown to be loyal to each other. Whether it's facing external threats or internal doubts in their relationship, they stand by one another. And the theme of shared dreams can also be found, like they might have a common goal for the future.
I like the fanfic 'Shinra and Tamaki: A New Beginning'. In this one, it starts with a new situation for both of them. It explores their feelings in a fresh way, like how Shinra first realizes his deeper feelings for Tamaki and how Tamaki responds to his newfound affection.
Another way is through their relationships. In the case of a Tamaki x OC fanfiction, their interactions with Tamaki are crucial. If the OC is initially shy around Tamaki due to her confident and outgoing nature, but gradually opens up, it shows character growth. Also, their relationships with other members of the Fire Force can contribute. Maybe they have a rivalry with one member that forces them to improve their skills, which in turn affects their overall character development.
One common trope could be 'opposites attract'. Tamaki might be outgoing while Shinra is more reserved, and this contrast can create an interesting dynamic in a love story. Another could be 'friends - to - lovers'. They start as friends, gradually realizing their deeper feelings for each other.
You can try websites like Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, and there's a good chance you'll find Tamaki and Shinra love fanfiction there.
The OC could be a scientist who is working on a new way to control the Infernals without having to kill them. Tamaki is assigned to protect the OC as there are those who oppose this new method. As they spend time together in the lab and during field tests, Tamaki becomes fascinated by the OC's intelligence and dedication. The OC, in turn, is charmed by Tamaki's positive attitude. They might face opposition from within the Fire Force, but their relationship and the OC's research continue to progress.
There's also 'A Blazing Bond'. In this fanfic, the OC has a unique power that ties into the existing powers in the Fire Force world. It delves deep into the relationships between the OC and the canon characters, exploring how they grow and change together. It's really engaging as it combines action and character - driven plotlines.
First, know the Fire Force universe well. Understand the rules about Infernals, the different Companies, and the powers of the characters. Then, create an OC with a unique backstory and personality that can fit into this world. For example, if your OC has a fire - related power, make it different from what already exists in the show.