I'm mainly doing this to torture my friend @HimikoTogaIsTheBest but it also sounded like a good idea in general. So here goes. In my AU the Hasahaki disease can start in anyone who is experiencing one sided love. But it can sometimes be caught by someone else who is in one sided love as well. Most of the time though it is just one and not contagious. But this may be the first time is centuries that it decided to be contagious. It is also very rare in general but most people have at least heard about it. They might not know what exactly happens to someone with it except that it can be deadly. They also may not know the signs of it but if you tell them what it is they will know.