Their relationship could develop if they are forced to rely on each other's skills. Lelouch is highly intelligent and strategic, while Cornelia is a skilled military leader. If they are in a situation where they need to combine their abilities to survive, like being stranded on an island or in a dangerous enemy territory, they might start to see each other in a different light. Over time, as they get to know each other's true selves, their relationship could evolve from grudging cooperation to something more like friendship and potentially love.
Realistically, their relationship could start from a place of mutual enmity. Since they are on opposite sides in the original story, any development would require a significant shift in circumstances. For example, if they are both betrayed by someone within Britannia, they might find common ground in seeking revenge or justice.
A possible plot could involve Lelouch losing his Geass powers and being captured by Cornelia. Instead of punishing him immediately, she decides to study him to find out more about the Geass. During this time, they engage in many deep conversations. Lelouch tries to convince Cornelia of the wrongdoings of Britannia's system, and Cornelia starts to question her own beliefs. This interaction could lead to a romantic relationship as they both grow and change through their exchanges.
For the OC, start by defining their backstory. Where are they from? What experiences have shaped them? If they are from a lower - class area in Britannia, they might have a different perspective on the empire compared to Cornelia. Then, think about their goals. Are they seeking revenge, justice, or something else? As for Cornelia, explore her loyalty to Britannia deeper. Show her internal conflicts, like her doubts about some of Britannia's actions. Also, in their interactions, let their characters evolve. For example, if the OC challenges Cornelia's beliefs, she could start to question herself more, and the OC could learn to be more diplomatic from Cornelia.
In many fanfictions, their relationship often starts from mutual respect. Kallen respects Lelouch's strategic mind, and Lelouch admires Kallen's strength. For example, in some fanfics, they start to rely on each other more during difficult battles, which deepens their bond.
In many fanfictions, their relationship starts from comrades in arms. They are both fighting for the same cause against Britannia. As they face more and more difficult battles together, they start to understand each other better and a deeper bond forms.
A fanfic about Cornelia could be a character study. It could delve into her past, like her upbringing in the imperial family and how that shaped her into the strong - willed person she is. Maybe it could also show her softer side that she doesn't often display in the anime.
A good Code Geass Lelouch fanfiction is 'Lelouch in a Parallel Realm'. In this story, Lelouch is transported to a parallel world where the power dynamics and politics are different. He has to adapt and use his wits in new ways. 'Code Geass: Lelouch's Alliances' is also great. It shows Lelouch forming unexpected alliances and how those relationships shape his journey. And 'The True Ending of Lelouch' is a fanfiction that tries to give a more satisfying and conclusive end to Lelouch's story.
A fanfic could center around Cornelia's relationship with her sister, Euphemia. It could show their sisterly bond, their differences, and how they support or oppose each other in the complex world of Code Geass.
Lelouch's character would likely become more cautious. Knowing the consequences of his past actions through time travel, he might think twice before making rash decisions. For example, he might not be as quick to use his Geass power without considering all the long - term effects.
The relationship can be developed through shared experiences. For example, they could be trapped together in a dangerous situation, like being stranded on an island. There, they would have to rely on each other for survival, which would force them to communicate and understand each other better.
A good one is 'Code Geass: Supernatural Shadows'. Here, Lelouch encounters a group of supernatural beings who are also involved in the power struggles of the world. He has to form alliances and make difficult decisions. The fanfiction is exciting because it combines the strategic elements of Code Geass with the mystery and otherworldly aspects of the supernatural elements.