Nearly 30 percent of people in common-law relationships in Japan have chosen not to marry because they do not want to change their own or their partner’s last name, as required by Japanese law, a recent private survey has shown.

The survey by Asuniwa, a nongovernmental organization advocating for separate surnames for married couples, found the rate was higher among people in their 20s at around 40 percent, with more than 60 percent of that group saying they would switch to legal marriage if separate surnames were allowed.

Demonstrators call for a law change in Japan to allow married couples to have separate surnames before the parliament in Tokyo on April 23, 2025. (Kyodo) ==Kyodo

The Justice Ministry says Japan, to its knowledge, is the only country that requires couples to adopt the same surname upon marriage.

While the main opposition Constitutional Democratic Party of Japan calls for introducing the option of separate surnames, conservative members of the ruling Liberal Democratic Party oppose the move, fearing it would affect traditional family values.

Yuichiro Sakai, an associate professor at Keio University, speaks at a press conference in Tokyo on April 21, 2025. (Kyodo) ==Kyodo

The NGO and Yuichiro Sakai, an associate professor at Keio University specializing in family sociology, conducted the online survey in March, covering 1,600 people aged 20 to 59, with 532 of them in common-law marriages, 538 legally married and 530 single.

Using the survey results and government population data, they estimated that about 1.22 million people in their 20s to 50s are in common-law relationships in Japan, with 587,000 of them wishing to marry if separate surnames are allowed.

Common-law couples do not have access to the same benefits legal couples have, such as spouse tax deductions and the statutory right to inherit their partner’s estate.

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