In a Giyuu x Shinobu fanfic, the setting and plot can vary widely. Some might be set during the main events of the Demon Slayer universe, with them facing demons together. Others could be more of an alternate universe story, where they meet under different circumstances, like in a modern - day high school AU. The fanfic could also delve into their backstories and how those experiences shape their relationship. For instance, Shinobu's past with her sister could play a role in how she opens up to Giyuu, and vice versa for Giyuu's own traumas.
I would recommend 'Whispers of the Heart' for Giyuu x Shinobu fans. This fanfic focuses on their unspoken understanding. It's full of small moments that build up their relationship, like when Shinobu leaves a small flower on Giyuu's doorstep as a sign of her care. Also, 'Shadows and Sunlight' is worth checking out. It has a great plot that involves them having to go on a secret mission together and how that journey changes their relationship from colleagues to something more intimate.
One common theme is the exploration of their relationship. Given their different personalities in the original work, fanfictions often focus on how they bridge the gap between them, like how Giyuu's stoicism and Shinobu's more cheerful yet calculating nature interact.
A 'cc0 visual novel' is a visual novel that comes with a very special license - CC0. The CC0 license is a powerful tool in the creative world. For visual novels, this means that the developers are giving up their rights to the work. It could be for various reasons. Maybe they want to contribute to the community in a big way, or they believe that their work could be improved and expanded upon by others. As a result, anyone can take the elements of this visual novel - be it the plot, the characters, or the overall design - and use them in their own projects. This can lead to a lot of new and exciting derivative works based on the original CC0 visual novel.
Adding CC to a story isn't too complicated. You could start by writing out what you want the captions to say. After that, find a platform or app that supports caption addition. Make sure to sync the captions with the relevant parts of the story for a seamless experience.
One common theme is the exploration of their contrasting personalities. Shinobu is often seen as more light - hearted and talkative, while Giyuu is quiet and reserved. Fanfictions usually play with how these differences can either create friction or bring them closer together.