One more theme that pops up a lot is the exploration of 'what - if' scenarios. Fanfic writers like to play with the idea of what would have happened if certain events in the series had been different regarding Lelouch and Shirley. For instance, what if Shirley had found out about Lelouch's true identity earlier? This leads to different relationship dynamics and storylines in the fanfics, which is really interesting to read about.
There's also 'Shirley's Choice' which focuses on Shirley's perspective in her relationship with Lelouch. It shows her internal struggle between her love for him and the complex situation he is in with his Geass powers and his goals. The story beautifully portrays her growth as a character while being in love with Lelouch.
You can start by looking on fanfiction.net. It has a large collection of Code Geass fanfictions, including many focused on the Lelouch x Shirley relationship. Just use the search bar and type in relevant keywords like 'Code Geass Lelouch x Shirley' and you'll find a bunch of stories.
Sure. One popular 'Code Geass Lelouch and Shirley fanfic' is 'A Different Path'. It explores an alternate timeline where Shirley's role in Lelouch's life is even more significant. Another great one could be 'Shirley's Choice' which delves deep into Shirley's character and her relationship with Lelouch in a really interesting way.
Yes, it is. As a 'Code Geass' fan, it gives you more content related to the series. You get to explore the story further and might discover new aspects of the characters and the world.
Code Geass did start as a manga. However, its anime version became even more widely known and beloved. The manga provided the foundation for the rich story and characters that were further developed in the anime.