Now You're One of Us was written by Asa Nonami.

The Shito family: eight people, four generations, one household, with young newlywed Noriko joining the clan to make nine. Her handsome husband, Kazuhito, adores her to distraction, while the rest of the family embraces her with open arms and a warm and generous spirit. The family is comfortably well off and it seems as if Noriko's happiness, now and in the future, is assured... Until, that is, she begins to suspect that her new in-laws' charming eccentricities may in fact contain hints of something more sinister.

As she probes deeper into their secrets and past, Noriko begins to see shadows around every corner, finding it harder and harder to tell which are real and which are merely the products of her own paranoia.