Another theme is the exploration of their contrasting personalities. Armin is often seen as the intelligent and more reserved one, while Reiner is the strong - willed and sometimes conflicted. Fanfics play around with how these differences can create an interesting dynamic between them, like in 'The Opposites Attract' fanfic where their differences actually draw them closer.
One popular Armin x Reiner fanfic is 'The Unlikely Bond'. It delves deep into their relationship, exploring how their different personalities complement each other. The story starts with them having to work together on a mission and gradually realizing their mutual respect and growing feelings.
Reiner did die in the manga. His death was a result of a series of events and conflicts that had been building up throughout the storyline. It had a major impact on the plot and the other characters.
In many 'Batman Beyond' fanfictions where Dana finds out, it could be about her finding out Bruce Wayne is Batman. Maybe she stumbles upon some evidence in the Batcave or notices some similarities in Terry's behavior to Bruce. For example, she might notice Terry's fighting style is similar to what she's heard about Batman's. It could also be that she discovers some secret technology related to Batman that leads her to the truth.
Well, one possibility is that Dark Naruto would be overjoyed. After all, Kushina is his mother. But at the same time, he could be very conflicted. His dark side might make him suspicious of her motives. He could test her in various ways to see if she's really who she says she is. And Kushina, on her part, would probably be heartbroken to see what her son has become.
In the fanfic 'Malfoy's Revelation', Malfoy is paired with Harry for a project. As they spend time together, Malfoy notices some strange behaviors from Harry, like flinching at sudden movements. After some snooping around, he discovers that Harry has been abused. This new knowledge makes Malfoy more empathetic towards Harry and he tries to help him in his own way, which includes standing up for Harry against some of their mutual enemies at Hogwarts.