In Japan married couples must have the same surname by law. Recently the introduction of ‘separate surname for married couples by choice ‘ is under discussion.

However, if the current system continues, the number of surnames will decrease by the number of married couples each year. It is estimated that there are 130,000 different surnames in Japan now. Currently ‘Sato’ is the most common surname in Japan, accounting for 1.5% of the Japanese population. That number is increasing year by year by marriages and childbirth.

According to the Research Centre for Aged Economy and Society in Tohoku University’s study if married couples continue to share the same surname, all Japanese people will have the surname ‘Sato’ by 2531″.