Japan is known for its variation of last names as Japan had 130,000 different family names in the Meiji period. However, due to the current practice of requiring married couples to have the same surname, the variety of Japanese last names is reducing gradually.
For the last April Fools’ Day, a professor at Tohoku University, Hiroshi Yoshida, published a simulation on the possibility of having one surname in the future with the current law regarding a married couple’s shared last name. This simulation was organized by the Think Name Project and Asuniwa to raise awareness of the consequences of not adjusting the current law.

Every Japanese Will Be “Sato” in 500 years
Currently, the most common surname in Japan is “Sato,” used by 1.53% of the population in 2023. This simulation used statistical calculations to find the year when everyone would have this last name, as it has a 1.0083% annual growth rate. The result showed that in around 500 years (by the year 2531), the population rate with the name “Sato” will exceed 100%. This means that there will only be “Sato” in Japan, losing individuality and unique identity.

On the other hand, the simulation also showed that if Japan implemented a law that allows people to decide whether they want to keep their surname or change it, this process would be delayed until the year 3310. However, the study also noted that the Japanese population might become extinct due to the continuous decline of the birth rate in Japan.
Related Issue Concerning Shared Surname in Marriage
Since 2014, Japan has been the only country that has a law forcing married couples to share one last name. This law is also enhancing gender inequality as 95% of wives change their surname to match their husband’s name. Therefore, other countries, such as Italy, Germany, Switzerland, and the States, have been adjusting their laws following the United Nations’ act towards gender equality. This project is also aimed at raising awareness of gender inequality caused by the law and social norms to change wives’ last names. Those people who change their name have to go through the process of changing the official document’s name as well as the separation of their career.
The April Fools’ Day joke successfully raised awareness of the law that forces married couples to share one last name and other potential problems caused by this law. This is a great opportunity to give it a thought.
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