Thirteen same-sex couples filed lawsuits across four districts in Japan Thursday alleging that the country’s denial of same-sex marriage is a violation of the Constitution.

During a news conference and march to the Tokyo District court, one of the plaintiffs, Kenji Aiba, explained that they are seeking ¥1 million in compensation and damages for emotional distress when government officials deny same-sex couples marriage licenses. Although some municipalities have passed partnership ordinances, the country as a whole has not recognized same-sex marriages as legally binding. This impacts the couples ability to sign consent forms for a partner’s medical treatment, inherit assets upon a death, or receive tax deductions.

The plaintiffs will challenge the country’s lack of recognition as a violation of Article 24 of Japan’s Constitution stating, “Marriage shall be based only on the mutual consent of both sexes and it shall be maintained through mutual cooperation with the equal rights of husband and wife as a basis.”

The government has interpreted the clause in civic and family law statutes to mean marriage between a man and a woman and the plaintiffs allege that the text does not explicitly define “both sexes” to mean opposite sexes. Some plaintiffs are also challenging the long held custom to be a violation of Article 14 as well which stipulates that “All of the people are equal under the law and there shall be no discrimination in political, economic or social relations because of race, creed, sex, social status or family origin.”

This is Japan’s first major challenge to the constitutionality of same-sex marriage.