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.