Participants march during the Tokyo Rainbow Pride parade on April 26, 2015. Reuters

A group of 455 lesbian, gay, bisexual and transgender Japanese people filed a human rights complaint Tuesday urging the Japan Federation of Bar Associations to legalize same-sex marriage. They want the federation, the nation's biggest, to look into the claim and eventually send a warning to the government in their favor, the Japan Times reported.

“If issued, the warning will be quite comprehensive, formulated based on the bar association’s meticulous research and analysis,” lawyer Toshimasa Yamashita told reporters. “It will likely be used as a reference in Diet [legislative] sessions or trials whenever the topic of same-sex marriages arises.”

The people behind the complaint were diverse: Their ages ranged from teens to people in their 60s. They argued that Japan's lack of explicit approval of same-sex marriage is unconstitutional because the country guarantees equality and dignity.

Japan doesn't ban same-sex marriages, but it doesn't recognize them either, often leading to discrimination and denial of benefits heterosexual couples receive, NHK reported. Only the Tokyo Shibuya ward codifies LGBT couples' rights, allowing them to jointly rent real estate and receive spouse visitation rights in hospitals.

Japanese Prime Minister Shinzo Abe said earlier this year that moving to allow same-sex marriage would require "extremely cautious consideration" because the constitution "does not envisage marriage between people of the same sex," the Guardian reported. A 2013 poll found that about 24 percent of people in Japan were in favor of legalizing same-sex marriage, with 27 percent opposing it.

The group of complainants Tuesday was hoping to capitalize on the LGBT rights discussion happening abroad. Yamashita said the bar federation may be more open in considering the complaint because of the United States Supreme Court's June 26 decision to legalize same-sex marriage in the U.S.