Same-sex couples in Hokkaido have appealed to the Supreme Court over a high court ruling that deemed the country's lack of legal recognition of same-sex marriage unconstitutional but rejected the plaintiffs' claims for compensation.

Earlier this month, the Sapporo High Court ruled that the failure to recognize same-sex marriage is unconstitutional, citing the equal guarantee of freedom under the Constitution for both same-sex and opposite-sex couples.

But the court rejected claims for compensation, saying that it could not be determined that the state had neglected to enact necessary legislation.

The plaintiffs appealed to the top court on Monday.

One of the plaintiffs, Nakaya Eri, who lives in Sapporo, said that despite the high court's ruling, discussions in the Diet failed to gain momentum.

She expressed doubt about the prospect of new legislation in the near future. But she emphasized the significance of obtaining a ruling of unconstitutionality from the Supreme Court.

A total of six similar lawsuits have been filed in five cities in Japan: Sapporo, Tokyo, Nagoya, Osaka and Fukuoka.

In the first and second-instance judgements, the ban on same-sex marriage was declared unconstitutional in three instances, deemed to be in a state of unconstitutionality in three cases, and found constitutional in one case.

This is the first time the issue has been taken to the Supreme Court.