It's not just women, but men also opt out of marriage. Because we have no reason for marriage anymore. The writer, as usual, don't mention the elephant in the room. It must be intentional because she probably want to write about women's right and nothing else.

The reason is nothing but for the lack of money. We, the average Japanese, cannot afford to have a child anymore. We just barely afford to have a life for themselves.

Why did we have to have a marriage? Because of the children. Because in the Japanese society, the children is assumed that they have a parent consists of one male and one female in marriage relationship.

Since we cannot afford to have a child, there is no reason to marriage anymore.

What other functions the marriage offer?

Asset management and inheritance? No. We can't afford to have a reserve or real estate. There is no use for that.

Bonding the families? No, as rural areas are more and more abandoned and everybody concentrate toward a few big cities, there is no traditional bonding of the families in one area.

Sex? Well, Not anymore. Japanese marriage system assume that the marriage is a exclusive sex relationship between single male and single female. It support very narrow traditional sexuality and excluding today's most of the sexuality.

The marriage system is now outdated. Ironically, the traditional marriage system is one of the cause of birth decline. It's an obstacle. Some people still want to have a child driven by natural instinct, but the current Japanese society assume a marriage between a male and a female who share their asset as the one, agree exclusive sexual relationship. Not following that pattern and you have huge negative impact on tax, school, health insurance and everything which makes those who want to have a child but don't agree on traditional marriage system holding to have a baby.

Conclusion: The marriage is outdated.