Explore the idea of redemption through their relationship. Vader's ultimate act of redemption in the original story was related to Luke, but in fanfiction, it could be Leia who also plays a part in that journey. Maybe Leia's unwavering belief in the good is what makes Vader start to question his own path more seriously, without changing who he is fundamentally as a powerful but conflicted Sith.
Another way is through the exploration of their family connection. Vader already knows he is Leia's father, but in fanfiction, he could be conflicted about how to handle this knowledge. Leia, on the other hand, could start to suspect something about their relationship. This internal conflict for both of them could drive the development of their relationship. They would still be on opposite sides in terms of the Rebellion and the Empire, but their personal relationship would be evolving in a very interesting and character - consistent way.
In some fanfiction, Darth Vader's full potential is explored through his relationship with other characters. For example, if he were to meet a powerful Force - user from another galaxy, it could trigger a growth in his abilities. This new acquaintance might teach him different ways of using the Force that he hadn't considered before.
In some fanfiction, their relationship might develop due to shared goals. Let's say they both want to stop a new superweapon being developed by the Empire. Working together towards this common objective forces them to interact more, and they begin to see each other in a new light. Vader might show moments of vulnerability, which Leia starts to pick up on, and she realizes there is more to him than just the menacing Sith Lord. This mutual discovery helps in building a more nuanced relationship between them.
One way is to have them communicate through the Force in a non - traditional way. Instead of direct conversations, they exchange emotions and memories. For example, Ahsoka could send Vader memories of their time together as master and apprentice, trying to stir the Anakin within him. Another unique exploration could be through dreams. They both have nightmares or dreams related to each other, which could reveal their true feelings and fears about their relationship.
Another way to develop their relationship is through a shared secret. Maybe they both know something about the Force that the rest of the galaxy doesn't. This secret brings them together in a way that defies their initial roles as Rebel and Sith. They have to communicate and collaborate to keep this secret, and in the process, their relationship evolves from pure hatred to something more nuanced, like a begrudging alliance with a hint of mutual curiosity.
Well, their relationship could start with mutual respect for each other's skills. Shan Yu respects Mulan's military tactics and Mulan respects Shan Yu's leadership among his men. This respect could gradually turn into a grudging admiration. For example, Shan Yu might admire how Mulan overcame so many obstacles as a woman in a man's army, and Mulan could admire Shan Yu's determination.
Well, there might be some darth vader and leia fanfiction out there, but the 'lemon' tag usually indicates something more adult - themed. I would suggest looking for more general, family - friendly fanfiction about their relationship instead. For example, stories that focus on their complex family ties in the Star Wars universe without the sexual undertones. It would be more in line with the spirit of the original story and also more widely accessible.
Since 'lemon' often implies adult themes, it's not appropriate to discuss. But in general non - lemon fanfiction about them might have themes like family, redemption, and the power of the Force. For example, the theme of family is huge as Vader is Leia's father, and their relationship is complex.
In an alternate universe, Darth Vader could be exiled from the Empire after a disagreement with the Emperor. He then stumbles upon Leia on a remote planet. At first, they are enemies, but as they are forced to survive together against various threats on the planet, they start to understand each other. Leia realizes that Vader is not all bad, and Vader sees in Leia a determination that he once had. This understanding could lead to a slow transformation of their relationship from hostility to friendship, and eventually, they could work together to try and bring about a new order in the galaxy, one that is not dominated by the Empire or the Rebellion but a more balanced one.
One way to further explore their relationship is through the Force. Since they are both strong in the Force, they could sense each other's emotions and intentions from a distance. For example, Vader might feel Ahsoka's determination to stop him, and it could remind him of her as a young Padawan. Also, a story could be written where they communicate through the Force without actually meeting, sharing memories and feelings about their past together.