Well, some characters might be amused. For example, Atsushi could be a bit shocked at first, seeing the different interpretations of Dazai in the fanfiction. He might find some of the more out - there scenarios quite strange but also interesting in a way.
One popular tomioka fanfic might be those that explore his backstory in depth. For example, there could be fanfics that focus on his early days of training and how he developed his skills.
One common theme is friendship. They often start as comrades in the Demon Slayer Corps and develop a deep friendship. For example, they support each other in battles.
Another way is to join fan communities dedicated to the series that tomioka is from. People in these communities often share and recommend great fanfics. For example, if he's from a well - known anime, join the anime's fan forum.
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.