Photo/Illutration Yoshihisa Aono, president of software company Cybozu Inc., holds a news conference in Tokyo’s Kasumigaseki district after the Tokyo District Court rejected his and other plaintiffs' lawsuit on March 25. (Ryota Kyuki)

The Tokyo District Court on March 25 rejected a lawsuit on allowing married couples to choose different surnames, ruling that legal provisions requiring a common name are constitutional.

Four plaintiffs, including Yoshihisa Aono, 47, president of software company Cybozu Inc., filed the lawsuit on Jan. 9, 2018, seeking a total of 2.2 million yen ($20,000) in damages from the central government.

They argued that the Family Register Law violates the constitutional guarantee of equality because it allows Japanese-foreigner couples to choose different surnames, but Japanese couples can only pick one common name.

However, the district court said the Family Register Law, which falls under the Civil Law, is constitutional.

The central government argued that a Supreme Court ruling in 2015 said Civil Law provisions requiring a husband and wife to share a common name were “constitutional.”

“Under the family register system, family relations are registered following the Civil Law,” the central government said. “It is impossible to revise the Family Register Law without revising the Civil Law.”

The four plaintiffs are all from the Tokyo area. Aono and another plaintiff chose their wives’ surnames upon marriage. The other two plaintiffs are in a common-law marriage.

Aono said the legal provisions forced him to use both his pre-marriage surname and registered surname for business purposes or private situations, “causing not only mental suffering but also a huge amount of economic losses.”