There are likely some out there. You could start by looking on fanfiction platforms like Archive of Our Own. Sometimes, these stories might explore the character of Dr Flug in difficult or 'hurt' scenarios within the context of the 'Villainous' universe. However, the availability and quality can vary.
Another option is to check out Tumblr. There are often fanfiction writers who post snippets or links to their full works on there. Search for 'villainous dr flug hurt' on Tumblr and you might find some interesting pieces, either directly on the site or through links to other platforms.
The kidnapper could be a power - hungry villain from another dimension. This villain has heard of Dr Flug's reputation and thinks that by kidnapping him, he can gain access to advanced technology. Or it could be a group of bounty hunters who were hired by someone who has a grudge against Dr Flug. They would capture him and deliver him to the person who hired them.
One possible plot could be that Dr Flug is kidnapped by a rival villain who wants to steal his inventions. Another plot might involve Dr Flug being kidnapped by an organization that wants him to work for them against his will. Or perhaps he's kidnapped by someone who has a vendetta against his boss and is using him as bait.
The Hashiras would likely show concern. Some, like Shinobu, would immediately start looking into possible medical solutions. Giyuu might be more reserved in his worry but would still keep a close eye on Tanjiro. The other demon slayers would also be affected. They look up to Tanjiro, so his sickness would lower the morale of the group. They would try to support each other while waiting for Tanjiro to recover.
I'm not entirely sure as 'bagless flug paperhat fanfic' seems like a very specific and perhaps made - up or very niche concept. It could potentially be a type of fan - created story (fanfic) that involves some unique elements like 'bagless' things and 'flug' (which might be a made - up term) and 'paperhat'. Without more context, it's hard to say more.
She could be very cunning. In many'read villainous princess novel', the princess uses her intelligence in a devious way. She might be good at hiding her true intentions and presenting a false image to the public while secretly plotting against her enemies. Also, she may have a sense of entitlement, believing that she is above the rules and norms of society because of her royal status.
Tanjiro might use his sense of smell to detect hidden threats. Since his sense of smell is super - enhanced, he could sniff out any demons or traps in the way of saving Rengoku. For example, if there are demons disguised as allies, Tanjiro would be able to tell by their scent.