The average annual income for women in Japan stands at around 30% - 40% below their male lequivalents — which is a powerful statistic. Although women have reached a largely equal footing with men in terms of legal rights, there remains a strong unspoken discrimination towards women in the workplace.
Women are largely expected to perform lower grade tasks and to leave employment upon marriage or the birth of children. Although there has been a slight shift in this trend over recent years, the changes are negligible. This issue is hotly debated within Japan with more pressure being brought to bear on employers to improve the situation but change has been slow.
Western women working in Japan will probably only encounter difficulties when trying to manage Japanese male colleagues - especially if they are older. Otherwise they will be accepted as an 'honorary man'.