I'm not entirely sure whether this is supposed to be a Higurashi spinoff, but right now I'm inclined to say that it isn't and that "Maebara Kei" is to "Maebara Keiichi" what "Furuwada Serika" is to "Furude Rika," just a bit more obvious. I wonder if Karen is supposed to be an expy of some other character? Like Satoko or Takano, maybe?