"Too bad the last I remember is from before we meet, though..."

She assumes it must surely be a bit awkward for him, after all! But, in any case, as to the matter at hand...

"I was thinking, actually," Ritsuka says. "If we can rule out the guests because it wouldn't benefit any of them, then isn't the opposite true of anyone who works here?"

That is, the staff are the most likely to have a motive to murder someone over an inheritance at risk of going to some stranger.