One idea could be a story where they are forced to team up on a dangerous mission in the demon slayer world. They start off not getting along well due to their different personalities, but as they face challenges together, they gradually understand and respect each other more.
Some dedicated Demon Slayer fan forums might also have fanfics or links to them. These forums often have sections where fans can share their own creative works, so it's worth checking them out for some unique Tomioka x Shinobu fanfic finds.
There was no clear connection between Sanguine Red's novels," Tengen " and " Tengen 1 ", which could form an independent series. However, judging from the name, Tengen could be considered a follow-up to Tengen 1 because Tengen was usually used to refer to the first work in the series. However, this was not absolute, because the name connection did not necessarily mean that there was a direct causality between the works.