One great 'shinobu and giyuu fanfic' is 'The Unspoken Bond' which delves deep into their complex relationship. It shows how they gradually come to understand and support each other in the face of various challenges in the Demon Slayer world.
First, study their characters. Know their personalities, backstories, and how they interact in the original story. For example, Shinobu is often calm but has a hidden fierceness, and Giyuu is a bit of a loner. Then, come up with an interesting plot. It could be about them going on a joint mission where they face a new type of demon. Keep in mind their relationship dynamics as you write.
There are fanfictions where Shinobu and Giyuu are paired in a post - demon - slaying world. For example, they might start a new life together, perhaps helping to rebuild the demon - slayer corps in a different way. Shinobu's medical knowledge and Giyuu's combat skills could be combined in interesting ways in these stories.
You can find 'demon slayer shinobu x giyuu fanfiction' on popular fanfiction websites such as Archive of Our Own (AO3). There are a large number of fan - created stories there, and you can search for specific pairings like Shinobu and Giyuu. Just type in their names in the search bar and you'll get a list of relevant fanfictions.
Spider - Man fanfiction often showcases the creativity of the fans. For instance, there are fanfictions that put Spider - Man in crossovers with other superheroes or even in different historical settings. I think it's a great way for fans to express their love for the character and expand on the Spider - Man universe that we know from the comics and movies.