I'm not entirely sure. Fanfic communities are vast and diverse. While it's possible that someone has written a fanfic with this concept, it could also be quite rare. It really depends on the creativity and interests of the fanfic writers within the Lelouch - related fandom.
C.C. is often a main character that interacts with Lelouch. Their relationship is complex and in the fanfic, they might continue to explore their connection, whether it's about the Geass or their personal feelings. Suzaku also could be a key character. He might have to come to terms with Lelouch being alive and they could either become allies again or have a more strained relationship.
Another aspect is the psychological aspect. Since both characters are complex, fanfics usually dig into their minds. They might show how Schneizel's calm and calculating nature contrasts with Lelouch's more passionate and impulsive side. This contrast can create a lot of interesting scenarios and internal conflicts within the story.
I highly doubt it. Given the disturbing nature of the theme (if it involves rape as the title suggests), it's not likely to be popular among the general audience who prefer positive and ethical content.
Since the idea involves such a disturbing concept as rape, it should not be promoted. Fanfics are supposed to be creative works within the boundaries of legality and morality. There's no value in exploring the details of this kind of 'fanfic'.
One common theme is the exploration of their complex relationship. They have a deep connection in the original series, and fanfics often expand on it, like delving into their trust issues. Another theme is the power dynamics between them, as CC has her own powers and Lelouch has his Geass.
The plot could involve Harry being reincarnated as Lelouch. He would bring his sense of justice from the wizarding world. He might use his Parseltongue ability to communicate with the Geass users in a unique way. And he could introduce magic into the Code Geass world, which would completely disrupt the existing power structures. For instance, the Emperor might see Harry's magic as a new threat and try to either control or eliminate him. At the same time, Harry could try to use Lelouch's influence to make the wizarding world more accepting of different species, just as Lelouch was trying to change the world in his own way.
They often show his internal conflict between his goals and his morality. Lelouch wants to change the world, but the methods he uses are often morally ambiguous. In a suicide fanfic, this struggle might reach a breaking point. He could be constantly thinking about all the wrongs he has committed in the name of the greater good. For example, he might be haunted by the memories of the people he has killed or manipulated. His Geass power also adds to his inner struggle. He may feel that the power has made him into a monster, and he can't live with that anymore, so he contemplates suicide as a way to end his inner turmoil.
In a 'lelouch is secretly a girl' fanfic, the plot could involve Lelouch's struggle with her identity. She may have been raised as a boy for strategic reasons. As she grows older, she starts to question her own identity. Meanwhile, her actions in the political and military arenas are constantly under scrutiny. When her secret is on the verge of being exposed, she has to make difficult decisions about who she really is and what she stands for. This could lead to a re - evaluation of all her relationships and her place in the world she has been fighting in.
The exploration of their relationship. It's not just about the obvious romantic or partnership aspects. It can also be about how they understand each other on a spiritual level. They both have complex pasts and the fanfics can really dig into how they come to terms with each other's demons.