As an ambitious graduate from an elite university, Kyoko Fukushima was aiming for the top when she got a job at one of Japan's big trading houses — often working late into the night alongside her male colleagues. Ten years and two kids later, she found her responsibilities downgraded to paper shuffling, so she resigned.

Now there's growing pressure on Japan's corporations to stop pushing working mothers like her to the sidelines and instead help them develop their careers. A new law that came into effect April 1 lays bare just how hard a task lies ahead. It requires large employers to publish statistics on their numbers of female employees and managers, along with plans for promoting them, complete with targets and time frames.

For Prime Minister Shinzo Abe, who's faced with a shrinking labor force and is opposed to a large influx of immigrant workers, keeping women at work is an economic imperative. While the number of women in employment has risen since he took office, many hold part-time and contract positions. He's set to announce a new package of family policies in May, but his previously announced target of having 30 percent of managers in all sectors be women by 2020 remains a long way off.