Thirteen homosexual couples in Japan filed a lawsuit Thursday against the government, demanding the right to marry.
They are suing for symbolic damages, arguing that the ban on marriage violates their constitutional rights.
If the courts agreed, it would mean that same-sex unions would have to be allowed in the future.
Japan is the only G7 country not to allow same-sex marriage, but surveys suggest strong support for the case.
The country's constitution stipulates that "marriage can only be done by mutual consent of both sexes" and the authorities have always interpreted it as not permitting same-sex marriage.
But Thursday's plaintiffs' lawyers argue that the text of the constitution was intended to prevent forced marriages and that nothing in this text explicitly prohibits same-sex marriage.
In turn, they argue that the denial of same-sex marriage is a violation of the constitutional right that all individuals should be equal before the law.
"A very conservative society"
The 13 couples will all file on Valentine's Day in different cities across the country.
One of the couples is Ai Nakajima, a 40-year-old Japanese, and Tina Baumann, a 31-year-old German.
The two are together since 2011, when they met in Berlin. After living in Germany for a few years, they moved to Japan. But living as a same-sex couple was very different in both countries.
"Japanese society is by nature very conservative," Nakajima told the BBC.
Many of their friends do not dare to call themselves homosexuals and hide their partner from family and even friends.
Japan is a very traditional country, but polls indicate that the vast majority of young Japanese are in favor of same-sex marriage.
Since 2015, some cities issue certificates for same-sex couples, but these are not legally binding and simply ask companies to grant equal treatment.
"So, while young people have overwhelming support for gay marriage, politicians tend to be older and are very hesitant when it comes to making a difference," he said. said Ms. Nakajima.
The group knows that the trials will obviously attract public attention on their fight, but they sincerely hope that they will succeed.
"We are ready to take the case to the Supreme Court," Nakajima said. "If we have to go that route, it could take more than five years."
German marriage rejected
They were married in Germany and shortly thereafter asked to have their marriage recognized in Yokohama, where they currently live.
As they expected, the German marriage was not recognized.
For both, it means real problems – Ms. Baumann is currently studying, but once she has graduated, she will have to get a new visa in order to stay in the country.
For a married couple, such a visa would be easily issued to a spouse – but this is not the case for same-sex partnerships.
The problems do not stop there though, explain the two women.
"In Germany it's much easier to go out and live the way you want," says Baumann.
"In Japan, however, gender roles are much more traditional and a woman should get married and have children.In many cases, one even expects a woman to stop working once that she became a mother. "
Many of their friends do not dare to talk openly to their families for fear of being excluded.
"It's almost as if you were banned," Ms. Nakajima said. "And it affects many aspects of your life – if you want to rent a house as a same-sex couple, for example, you may be rejected for that reason, or you may not be able to take out a loan. as a couple to buy a property together. "
"It's really like in almost every situation we encounter problems," she says.
"We have received criticism from the public that we should simply move to Germany rather than create problems here in Japan," said the German.
However, they finally decided that it was more important to defend their beliefs.
Thursday's trial will likely be just the first step in a long process to allow same-sex couples to marry in Japan.