Her relationship with Lelouch would also change. If she travels to a time before she knew him well, she might view him differently at first. And if she travels to a future where their relationship had different outcomes, she would have to reevaluate her feelings for him. This would add more depth to her character as she struggles with her evolving relationship with Lelouch and her own identity within the story.
Kallen might also develop a stronger sense of leadership. In a new time period, she may have to take on different roles and responsibilities. This would force her to grow as a leader. She could learn new strategies and ways of dealing with people, which she could then bring back to her own time to better lead the Black Knights.
Another possibility is that Kallen travels to a time when the Geass power was first discovered. She might get involved in the events that led to the creation of the Geass and try to change the way it was used. Maybe she could stop certain individuals from getting Geass powers that were misused later. This would change the whole power dynamic in the Code Geass universe.
Their relationship could develop through shared goals. For instance, if they both aim to overthrow a corrupt regime within Britannia. Working side by side towards this common objective would make them rely on each other, leading to mutual respect and eventually love.
This fanfic idea presents a very interesting twist on the original Code Geass story. It would be exciting to see how the story unfolds with Kallen on the side of Britannia. Her skills and abilities could be used in different ways. For example, she could use her piloting skills to fight for Britannia against new threats, which would completely change the power dynamics in the Code Geass universe.
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.
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.
It could include their courtship. For example, Lelouch might start to show his softer side to Kallen, and she in turn would be more open about her feelings. They could go on secret dates in the rebuilt areas of the world, away from the prying eyes of the public. The fanfiction might also show how their friends react to their relationship. Some might be supportive, while others might be skeptical at first but then come around.
One possible fanfiction could be a post - war scenario. After the chaos and destruction in the Code Geass world, Lelouch and Kallen, having fought side by side, realize their deep connection. They start to rebuild the world together and gradually their friendship turns into love. Eventually, they get married in a small, private ceremony attended by their closest friends and allies. The fanfiction could focus on how they overcome the differences in their backgrounds and the challenges of leading a new world while being in love.
In a Code Geass Lost Colors Rai x Kallen fanfiction, Rai could be in a situation where he has to protect Kallen. This could lead to some intense and emotional moments. Maybe Rai discovers a side of Kallen that she doesn't show often, like her vulnerability. Their relationship could grow as he becomes her confidant and protector, and they face the challenges of the Code Geass world together.
The 'Code Geass Kallen Expansion Fanfic' is probably about taking Kallen's character from Code Geass and building on it. It could be a story that gives more screen time to her motives. Maybe it shows how she became so dedicated to the cause of the resistance. It could also detail her relationship with Suzaku from a different perspective. It might add more depth to her character by showing her making difficult decisions that were not shown in the original series and how those decisions shape her future in this fan - created expansion.
C.C. might view it with a sense of detachment at first. But then she might realize that Lelouch is becoming more attached to Kallen in a way that could potentially change their own relationship. She might start to feel a bit left out or even jealous, as she has been by Lelouch's side for a long time and has her own unique bond with him.