Another theme could be sacrifice. In the original story, both Bertholdt and Annie have to make difficult choices for the sake of their mission. Fanfictions might expand on this, showing how their relationship is tested by their need to sacrifice for their homeland. For example, a story could show Bertholdt's internal struggle between his feelings for Annie and his loyalty to Marley when he has to make a crucial decision. This can add a lot of emotional depth to their relationship.
The theme of redemption can also be present. Given the actions they've taken in the main story, some fanfictions might explore how they could find redemption through their relationship. Maybe they try to atone for their past deeds together, or their love for each other becomes a catalyst for them to change and seek a different path than the one they were originally set on in the context of the war between Marley and Paradis.
I'm not sure about specific fanfictions off the top of my head, but you could also check out fanfiction.net. Some of the fanfictions might explore their relationship in depth, perhaps delving into their shared experiences as Warriors and how that affects their connection with each other. It's a great place to start exploring different takes on their relationship.
One common theme is loyalty. Given their roles in the story, fanfictions often explore how loyal they are to each other, whether it's in the face of danger or moral conflict. For example, in many stories, they will stick together no matter what decisions they have to make.
The theme of trust is crucial in 'Attack on Titan Reiner x Bertholdt fanfiction'. They have to trust each other completely in order to survive in the harsh world of Titans. Additionally, the theme of redemption sometimes shows up. If they make mistakes or have actions that they regret, they try to redeem themselves in the eyes of each other and also within the context of their friendship.
One popular theme is redemption. Since Annie has done some not - so - great things in the original story, fanfictions might explore her journey of redemption through her relationship with Eren. Another theme could be forbidden love. Given their different allegiances in the story, a relationship between them would be considered taboo. Also, the theme of power balance is common. They both possess unique Titan powers, and fanfictions could play with how they interact with each other in terms of power, like whether they compete or cooperate.
One popular 'Attack on Titan Bertholdt x Reiner fanfiction' is 'Beyond the Walls of Duty'. It delves deep into their complex relationship, exploring their shared experiences and the unspoken bond between them. The story often shows how they support each other during their difficult missions within the context of the 'Attack on Titan' world.
The contrast between their characters. Annie is strong, stoic and a bit of an enigma, while Armin is more cerebral and empathetic. Their interactions can be really fascinating to explore in fanfiction.
In a crossover fanfiction, Naruto's sense of justice might conflict with Annie's actions in Attack on Titan. Naruto always tries to find a non - violent solution first, while Annie has been involved in some pretty brutal acts. This could lead to some great character development and interesting plot twists. Also, the different power systems of the three franchises could create unique battle scenarios, like a fight between Naruto's Rasengan and Annie's crystal - hardening abilities.
One common theme is redemption. Annie has done some pretty bad things in the series, and in many fanfics, Armin is a key figure in her journey towards redemption. Another theme is love in the face of chaos. Given the world they live in, filled with Titans and danger, their love is often portrayed as something that can survive and even thrive in such a harsh environment. Also, the theme of understanding each other's pasts is quite common. They both have complex backstories, and fanfics often explore how they come to understand and accept each other's past traumas.
There's a fanfiction named 'Reiner and Bertholdt: A Different Path'. In this story, it takes a different turn from the original plot and focuses more on their relationship outside of the main battles. It shows their more personal side, like how they interact when they are alone. And 'Hidden Feelings' is also a good one. It delves into the emotions that Reiner and Bertholdt might have for each other but keep hidden from others.
One popular story might be about their unlikely friendship evolving during their time in the military training. It could explore how Annie's tough exterior starts to crack in the presence of Armin's gentle and intelligent nature.