The problem isn't so much the sex is it? The problem is of course demographic. Related, but not the same. Amazingly the government of Japan surely understands the problem at hand, and still refuses to act. Labour laws of course cannot allow an employer to fire someone (or choose not to hire) based on pregnancy (or being a woman of that age). There is only one sure way of making women as desirable to hire in this respect: ensure men stay at home with children just as much as women. State subsidized childcare and a year or two of paid maternal/paternal leave per child would be a net win for Japan (as it is for most such countries).