I can't be the only one that spent the entire story wondering what happened to Remi and Flan, can I?
But, eh, decent take on a common plot
It's not just you, I couldn't figure out why the author even mentioned it. Certainly Meiling and Sakuya didn't seem particularly fussed, which is a bit odd for Sakuya at least.
Still, really good study of the two of them. Reminiscent of the last chapter of MariAli.
maybe they moved or passed away (unlikely), no explanation. another possibility is that Meiling is pretending or doesnt want to know, it is clear the mansion is abandoned since no one comes to visit anymore (which could imply that something happened to the usual visitors as well.)
But see, that's what gets me. Why even bring it up? It's pretty significant that Remi went to Flan's room and neither were seen again, and mentioning that in-story makes the reader curious as to what happened. If it's not mentioned, the reader can just assume they're off stage somewhere and not worry about it.
In any other story the vampires vanishing would be as much an incident as them appearing in the first place, don't you think? Certainly not something that would be greeted with "welp, these things happen" by those loyal to them.