Writing sexual fanfic, especially when it involves non - consensual or inappropriate use of characters, is not appropriate. It goes against ethical and respectful creation of fan - made content.
I don't know exactly. It could depend on the specific manga universe or storyline. Maybe you can search through popular manga forums or fan communities for the answer.
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.
A common theme is the power of their combined strength. Tanjiro has his own set of skills and Mitsuri has hers. Fanfics often explore how they use their combined powers to defeat powerful demons. Additionally, the theme of hope is often present. Their relationship gives them hope in the dark world of demon slaying, and they inspire others around them with their positive attitude and connection.