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.
A popular plotline is when there's a new girl who has a power that complements Deku's really well. Uraraka sees them interact and gets jealous. She may start to doubt her own worth and place in Deku's life. In response, she could either become withdrawn or go on a journey of self - improvement to be more confident and show Deku that she's the one for him.
Uraraka might be jealous of someone who has a more powerful quirk than her and is getting more attention from Deku. So she decides to train secretly to improve her quirk. After some time, she shows off her new skills and gains Deku's admiration again.
One possible analysis could be that their relationship in fanfic often showcases a strong bond of friendship. Bakugo's explosive personality and Kirishima's more stable and friendly nature create an interesting dynamic. Fanfic writers may explore how they support each other during battles or in their daily lives at school. For example, Kirishima might be the one to calm Bakugo down when he gets too riled up, and Bakugo could inspire Kirishima to be more confident in his abilities.
Kirishima is still alive in the manga. The story doesn't have that plot point. Usually, character deaths are significant events and are clearly shown if they occur.
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.