the term doesn't exist, since Japan doesn't really have a need for gender-nuteral terms in the way we do. only truly semi-agreed-upon term for gender neutrality in Japan is "X", as in "Xジェンダー" (https://ja.m.wikipedia.org/wiki/Xジェンダー)
i should mention that "Xジェンダー" isn't *just* for nb persons. it's a term used for EVERYONE outside the gender norms, because there's no need to make such specific distinctions in the japanese language and culture.
thank you :]] she is truly peak of evolution