Everyone in Japan will be called Sato by the year 2531 because of the country’s marriage laws

  • Japan is the only country that requires spouses to use the same surname
  • The surname Sato represents approximately 1.5 percent of the country’s population

In 500 years, everyone in Japan will have the surname Sato thanks to the country’s current marriage laws.

If the practice of requiring married couples to share the same surname – rather than keeping their birth name – continues in Japan, there may be no other surname left by the year 2531.

Japan is the only country in the world that requires spouses to use the same surname, according to an archaic civil code from 1898.

As of 2023, Sato was the most common surname in Japan, accounting for approximately 1.5 percent of the country’s population.

An economics professor at Tohoku University, Hiroshi Yoshida, has predicted that if this continues, the only surname left will be Sato, which will inevitably lead to social chaos.

The surname Sato is predicted to be the only one left in Japan in 2531, thanks to archaic marriage laws requiring spouses to use the same surname

In the scenario, every sports team, classroom and office would be named Sato-san.

But this result is said to be a product of Japan’s marriage laws, which require Japanese people who marry to adopt the surname of one or the other.

In 95 percent of cases, this means women give up their maiden name and take their husband’s name.

About 500,000 new marriages are registered in Japan every year, meaning almost half a million people lose their surnames every year.

Sato’s annual growth rate is reportedly increasing by 1.0083 percent according to data collected between 2022 and 2023.

In Japan, more than 5% of the country’s population shares only four surnames: Sato, Suzuki, Takahashi and Tanaka.

If no changes are made to current legislation, the hypothesis suggests that by 2246, 50 percent of surnames will be Sato.

A series of legal challenges have failed to overturn the marriage laws we have in Japan today, even after several complaints emerged highlighting that they disadvantage women who have built their careers under their maiden names.

Until Yoshida’s research, however, no one had fully recognized Sato’s seemingly unstoppable rise—and the consequences its takeover could have on society.

Yoshida told Japanese newspaper The Mainichi: “If everyone becomes Sato, we may have to be addressed by our first names or by numbers.

“I don’t think that’s a good world to live in.”

A country full of Satos “will not only be troublesome, but also undermine individual dignity,” he said in an interview with the Japanese newspaper Asahi Shimbun.

‘This would also lead to the loss of family and regional heritage associated with surnames.’

The study, using 2022 Japan Trade Union Federation data, also found that if different surnames were allowed, it would delay the possibility of one dominant name to 7.96% by 2531.

But they suggest that due to the declining birth rate, Japan’s population is predicted to be extinct by then.

The research was supported by the Think Name Project, a group that advocates for a change in the selective single surname system.

Groups calling for a change in the law on married names hope their campaign will be boosted by the possibility that names like Suzuki and Yoshida – the 11th most common name – could one day be wiped out.

Yoshida’s research was reported on Monday and many assumed it was an April Fool’s joke, but the professor said he wanted to get people thinking about the shocking – but very possible – scenario.