Claiming that it is unconstitutional for Japan to not recognize same-sex marriage, 13 lesbian and gay couples on Thursday filed lawsuits against the government.

In the first legal challenge of its kind in Japan, couples of various age groups, from their 20s to 50s, simultaneously brought suits to district courts in Nagoya, Osaka, Sapporo and Tokyo on Valentine's Day.

They are each demanding ¥1 million in compensation with an additional holdback worth 5 percent of the damages sought until the payment is complete, as well as funds to cover litigation costs incurred during the process.