A lot of MHA Kaminari x Jirou fanfictions focus on the idea of mutual understanding. They come from different backgrounds and have different quirks, but through getting to know each other better, they grow closer. There are also themes of jealousy, like when one of them might get a bit jealous if the other is spending too much time with someone else. Also, their shared experiences at UA, like going through tough battles together, are often used as a theme to bring them closer in the stories.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). There are a ton of MHA fanfictions there, and you can specifically search for Kaminari x Jirou ones. Another option is Fanfiction.net, though the quality can be a bit more variable. You could also check out Tumblr, as some users post links to their favorite fanfictions or even write short ones themselves.
In some BNHA fanfics, Kaminari might be portrayed as the traitor, but it really depends on the specific plot and the writer's creativity. There are various interpretations in the fanfic world.
Denki Kaminari remains alive throughout the manga. The author didn't include his death as part of the narrative. His character has continued to play an active role in the story without facing such a fate.
A popular 'bnha kaminari fanfic' usually has a strong focus on his character. It might explore his unique quirk, like his electricity - based powers. For example, it could show him learning new ways to control or enhance it.
One great kaminari x shinsou fanfic is 'Electric Bonds' which explores their relationship in a really interesting way. It shows how their different quirks interact and how they start to understand each other on a deeper level.
In some fanfictions, Kaminari might be portrayed as the traitor, but it's not a common or canon concept. Fanfiction authors often like to explore different plot twists, so they may choose an unexpected character like Kaminari to be the traitor just for the sake of creating a unique story.
There are kaminari fanfics that place him in alternative universes. In some, he might be a villain instead of a hero. This completely changes his character dynamics. Writers explore how his powers would be used differently in such a role, and how his relationships with other characters would be affected. It's really fascinating to see these different takes on his character in fanfic.
A common theme is self - discovery. When Kaminari snaps, it often leads to him realizing new aspects of himself, like his true power levels. Another theme is the struggle with control. His snaps are often associated with a loss of control over his electricity, and fanfictions explore how he regains that control.