Nobuko Kobayashi writing for Nikkei Asian Review:
Women are expected to use separate vocabulary and more demure tones.
Japanese is one of the languages where nouns may not be gender-specific, as in German or French, but the language constructions themselves would differ when used by men or women. Japanese women habitually use a different pronoun for "I" and choose the language that is less assertive and more polite.
Women are softer spoken and use more euphemisms. Unwritten rules around women's language reflect the acceptable features of women in Japan: never direct, always respectful. In a business context, even a senior-ranking woman would intentionally speak demurely to a male peer with a soft, soothing tone.
Japanese is inherently more subtle than Western languages. Japanese speakers often avoid describing matters directly. When Japanese women are culturally expected to talk even more delicately, the result is often practically incomprehensible to a foreign ear.
Compare, for example, these expressions that really aim to convey the same meaning: "These numbers are wrong" vs "I am afraid I am just not good with numbers. Could they really be correct?"
Imagine how differently a Westerner would react depending on which expression their colleague or subordinate used.
In the Japanese workplace, gender difference is no less evident in the language men and women use than in, say, their dress code.
