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.
The Quinx Squad could react with a mix of respect and wariness. They respect power, and Kaneki has a lot of it. However, they are also loyal to their cause of protecting humans from ghouls. Meeting Kaneki would force them to re - evaluate their views. They might start to question whether all ghouls are truly bad, especially when they see that Kaneki has his own moral code. This could create internal conflict within the squad as they try to figure out how to deal with Kaneki.
Harley Quinn might get really into it. She has a wild and unpredictable personality. She could start to role - play some of the scenarios from the fanfiction in real life, much to the confusion or amusement of the other Squad members. It would be in - character for her to embrace this strange new view of their world.
At the moment of the body swap, Aladdin would likely be stunned. He'd be like 'What just happened?' as he looks down at his now - female form. He might feel a bit self - conscious about the new body and the different clothing. Jasmine would be equally shocked. She might be more vocal about her dismay, exclaiming something like 'This is unacceptable!'. But then, being the strong - willed character she is, she'd quickly compose herself and start to assess the situation, thinking about how to get out of this predicament while also trying to understand what Aladdin usually goes through in his daily life.
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.
Amateur couples often experience a mix of excitement and anxiety. The excitement comes from the novelty of the situation, but the anxiety is due to the fear of the unknown and potential negative impacts on their relationship. For instance, they might worry about how their partner will interact with the new person, or how they themselves will handle the new relationship dynamic.