One interesting 'demon slayer reaction fanfiction' could be about the characters' reactions to modern technology. For example, Tanjiro might be amazed by a smartphone and its functions. Another could be their reactions to different types of food from our world. They might find pizza or ice cream very strange but delicious.
First, know the characters well. Understand their personalities, like Tanjiro's kindness and determination. Then, think of an interesting situation for them to react to, such as meeting a powerful new demon. Keep their reactions in line with who they are. For example, Zenitsu would probably be scared at first but then find some courage.
There are a few novels that I can recommend to you. They are all stories about being reborn as a Demon Slayer. The first was "Rebirth of the Sea of Laws, I Slay Demons in the Human World" and "Rebirth of Slaying Demons, I Actually Became a Demon Venerable?" They all focused on slaying demons and told the story of the protagonist becoming a demon slayer after his rebirth. In addition, there was also "Xu Xian's Demon-slaying Daily Life (Demonic Meow)" and "Black Moonlight of the Rebirth of the Demon Lord," which also involved the demon-slaying plot. These novels all have different styles and storylines. You can choose to read them according to your preferences.
Definitely! Demon Slayer started as a manga. It's known for its compelling plot and well-developed characters. The manga provides the foundation for the success of the anime adaptation.
One possible reaction in a fanfiction could be about the new dragon species introduced. A character might be in awe, thinking 'These dragons are so unique! Their colors and abilities are like nothing I've ever seen in Berk.'
One interesting Goblin Slayer reaction fanfiction could be where the characters react to a modern - day weapon being introduced into their world. It adds a new and exciting twist to the story.