Plaintiffs contesting family laws that require spouses to choose a single surname expressed shock and anger at Wednesday's Supreme Court ruling, saying it sets a bad precedent and will force more women to suffer the misery of having to change their name upon marriage.

In a vote of 10 to 5, the nation's top court dismissed claims by five women seeking the right to retain their maiden names after marriage. The court said the century-old Civil Code provision requiring couples to share a surname — they can choose which — is "established in Japanese society," and that the matter should be taken up in the Diet, not the courts.

"I'm sad, I'm in pain," a weeping plaintiff Kyoko Tsukamoto told a news conference in Tokyo following the ruling. She goes by Tsukamoto, her maiden name, although her husband's name must be used on legal documents. "My name is something I can't give up."