In the second World War when men had to leave, most of the women worked as a domestic. Following that they were regulated to office work.
In that time women wanted to work to help their husbands to supplement the military incomes. They worked in the manufacturing industry, with this women could have more opportunities, and as a result the Japan economy had grown.
Even after the war women still had jobs, the biggest reason is because Japan wanted the economy to increase, and women won rights because of that.
