A Tokyo court ruled on Wednesday that a ban on same-sex marriage was constitutional but said the lack of legal protections for same-sex families violated their human rights, which plaintiffs welcomed as a step toward aligning Japan with other Group of Seven nations.

Japan is the only G7 nation that does not allow same-sex marriage, and its Constitution defines marriage as based on "the mutual consent of both sexes." The ruling party of Prime Minister Fumio Kishida has yet to disclose plans to review the matter or propose legislation, though several senior members support same-sex marriage.

"This is actually a fairly positive ruling," said Nobuhito Sawasaki, one of the lawyers involved in the case.