A Shizuoka couple in their 20s filed a lawsuit Thursday over the six-month ban on remarriage for newly divorced women, calling it unconstitutional. They are seeking ¥3 million in compensation.

A related measure has left the couple's 5-month-old son without a koseki entry in the family register, plunging the boy into legal limbo and potentially depriving him of education and recognition by the state.

Despite living together as if they are married, the woman, who divorced her former husband in May, has one month to go before she can formally marry her new partner. The ban ends in November.