Any thoughts on the manga-ka of InuYasha, Ranma, and Maison Ikkoku?
My first guess is ISTP.
50 Questions for Rumiko Takahashi | SUNDAY Feature Articles
I think she is a xxTP for sure. Her most famous series, though beloved by their fans, were often criticized for rambling on and not having a clear direction. She starts things, sometimes works on them sporadically, and struggles to finish. No way she is a J; no one with an ounce of J in them would have written stories as long as InuYasha and Ranma.
The T vs. F thing comes from what she focuses on the most in her series, and also the linked interview above. To use InuYasha as an example again, I feel that the romantic subplots of that series would have been far more central or blatant if she were an F. God, I'm an NT and I wanted to see more out-and-out sappy stuff in her work sometimes!
Also Rumiko says "No" to the question "Are you a person of clear and distinct emotions?" which suggests more T over F.
Her lack of interviews/information on the web, for someone so famous, suggests she is reclusive to a degree (I).
And finally, if we take it that she is an IXTP, her works appear to strongly favor S over N. Unlike what I would imagine an INTP writer to be like, Takahashi doesn't seem to get too...contemplative in her stories. They are more like "well that happened to said characters, let's move on to the next thing!" Not to come across as some MBTI racist, but an INTP writer would touch on more abstract and philosophic topics.