As of the latest chapters, Izuku and Uraraka have shown some mutual interest and closeness, but it's not a definite romantic pairing yet. It's still evolving in the story.
In some fanfictions, new original characters are introduced. These new characters are designed to be a potential threat to Uraraka's relationship with Deku. They might be transfer students with amazing quirks who immediately take an interest in Deku. Uraraka then sees this new character getting close to Deku and becomes jealous, leading to various conflicts and emotional drama in the fanfiction.
Well, in a fanfiction about Uraraka's jealousy, it could be that there's a fan event where Deku is paired with another hero - in - training for some sort of activity. Uraraka, seeing them together, feels a pang of jealousy. She tries to hide it, but her actions give her away. For example, she might be a bit short - tempered with others. Her jealousy could also drive her to work on her own skills more, not just to be a better hero, but also to be more appealing to Deku. As the story progresses, she might learn that jealousy isn't a healthy emotion and that she should focus on her own growth and relationship with Deku in a more honest way.
In a midoriya x uraraka fanfic, the author might play with the idea of their unspoken feelings. Uraraka's admiration for Midoriya could be delved into deeper, and Midoriya's possible realization of her importance in his life. It could also include some cute moments like when they train together or share a meal, which would add a lot of charm to the story.
Typically, these fanfics often focus on their relationship, whether it's friendship or a budding romance. They usually incorporate elements from the original 'My Hero Academia' universe, like their hero training and the challenges they face at school.