Well, fanfiction about Euphemia and Lelouch often explores their complex relationship. In the original Code Geass, their relationship was full of political and emotional entanglements. Fanfictions might expand on the unfulfilled potential of their relationship, like imagining a world where they could have overcome the barriers between them, perhaps in a more peaceful world without the chaos of war and power struggles.
One common theme is the exploration of gender roles. Since Lelouch is female in these fanfics, it often challenges the traditional male - dominated power dynamics in the original Code Geass world. For instance, a female Lelouch might have to use different strategies to gain power and respect.
There is a fanfic called 'Lelouch's Time Travel Adventure'. In it, Lelouch travels back in time to a point before the start of the series. He uses his knowledge of the future to try and prevent the events that led to the sad state of the world in the original story. It has some really cool moments where he outsmarts his enemies using future knowledge, and the way the author writes his internal monologues is very interesting, making it a great read for Code Geass fans.
Yes, there are quite a few. You can start by looking on fanfiction platforms like FanFiction.net or Archive of Our Own. Some fanfics might focus on Lelouch's new life after the events of the series, exploring his relationships and new adventures.
One common theme is redemption. Since Lelouch has done many morally ambiguous things in the original series, some fanfics focus on him trying to make up for his past actions. Another theme is love and relationships, such as his relationship with C.C. or his sister Nunnally.
Power dynamics is also a theme. Euphemia was a princess and Lelouch was a revolutionary in a way. Fanfictions may explore how their relationship affects the power balance in the world of Code Geass. It could be about them using their combined influence for good or the struggles they face because of their different positions of power. And also, the theme of sacrifice might be present, as they both had to make sacrifices in the original story, and fanfictions can expand on that concept in relation to their relationship.
There's also 'The Unspoken Bond'. In this fanfiction, the author delves deep into the unspoken feelings between Kallen and Lelouch. It starts with small, subtle moments between them during the battles and gradually builds up to a more complex relationship. It's a great read for those who love to analyze the characters' emotions.
One popular 'Code Geass Lelouch Fem Fanfic' is 'The Empress of Britannia'. It explores an alternate universe where Lelouch is female and has to navigate the complex political and power dynamics in a very interesting way.
Another option is Wattpad. Although it has a more general audience, there are still some good Code Geass fanfictions there. You can try searching for the relevant keywords and then look at the reviews and ratings of the stories to determine if they are worth reading.
One great fanfiction could be about Lelouch and CC going on an adventure outside of the main plot's battles. They might discover a hidden land where they have to rely on each other in new ways, deepening their bond. Maybe they find a magical artifact that only CC can understand, and Lelouch has to protect her while she figures it out.