If fushimi found out that he have the same sickness that his father had ... you think he would refuse treatment? Or think that he have it because he is a bad person like he father was, like he deserves it?
Technically we don’t really know what kind of treatment could have helped Niki, all that’s said in LSW is that he had a disease of his internal organs due to neglecting his health and in the all characters story Kisa suggests looking for an American hospital where presumably he might have been able to receive some kind of experimental or high level treatment. So that being the case I wonder if Fushimi came down with the same kind of illness if he might refuse treatment just because he believes there’s no point to it, Niki had all this money and access to quality care and he still died so maybe Fushimi should just embrace the inevitable and let himself die too. I think he’d probably take receiving the diagnosis really poorly, like even post-ROK when Fushimi’s slowly starting to realize that he’s not like his father and that he’s worthy of being cared for he would still have a moment of pause hearing that he is indeed following in ‘that man’s’ footsteps and is probably going to die a miserable death the same way. I think he wouldn’t want to tell anybody, thinking that he’s going to be pitied somehow, and he’d probably have a sort of bitter amusement at the whole thing, like he tried so much to not be worthless like Niki and in the end he still got stuck with the same fate, how stupid is that. But then at the same time he’s surprised to realize that he’s scared of dying like Niki too, like he’s started letting people close to him and the idea of dying all alone in a hospital bed is terrifying and Fushimi doesn’t know why, doesn’t know why he was able to accept the idea of dying alone in jungle’s hideout but the idea of being killed by this disease just fills him with dread. And then meanwhile the rest of the cast starts noticing that Fushimi looks paler than normal and maybe he’s coughing a lot and seeming weak, and then finally one day he collapses while out on a mission. He wakes up in Scepter 4’s infirmary surrounded by most of the rest of the cast and Yata especially is very loudly pissed that Fushimi didn’t tell anyone he was sick, like what the fuck you stupid monkey do you want to die and Fushimi’s just staring at him blankly wondering why Misaki’s crying.