Everyone in Japan will be called Sato by 2531 unless marriage law changed, says professor

Sato will become the only option by 2531, suggests modelling as part of campaign to overturn outdated law requiring spouses to have same surname

Japanese citizens will all have the same family name in 500 years' time unless married couples are permitted to use separate surnames, a new study has suggested as part of a campaign to update a civil code dating back to the late 1800s.

The study, led by Hiroshi Yoshida, a professor of economy at Tohoku University, projected that if Japan continues to insist that couples select a single surname, every single Japanese person will be known as Sato-san" by 2531.