I was discussing with a friend, who asked me if 忍者 is also used for women, or if くノ一 is used/preferred. I know 者 means "person", so it seems to be neutral; and Weblio defines the word using 者, which again seems to suggest it can be used for women; but I noticed in Basilisk female characters are called 女忍者.
I wasn't able to find something definite about this: can 忍者 be used for women, or does it sound strange/wrong?
Edit: Another friend of mine said that 忍び is used for men, but weblio doesn't say anithing about that, and it being an abbreviation for 忍びの者 it does seem neutral; not sure if it can also be used for women.