With gay marriage banned in Japan, Takashi Otsuka saw so few legal options that he decided to legally adopt his same-sex partner.

Otsuka, 74, who has run a bar in Tokyo’s Shinjuku Ward for 40 years, met his partner, Shinji, 51, when he came to his bar as a customer 20 years ago.

Before long they moved in together. But because of the large age gap between them, Otsuka decided to adopt Shinji as his son in 2013 so he could leave him his money if he died.

Under the law, two people cannot legally marry after they dissolve an adoption. But Otsuka said that back then, he had no hope they would ever become legally married in Japan, whereas the adoption system would firmly protect their relationship as a family.

Otsuka, however, is much more optimistic now that the Tokyo metropolitan government is introducing a partnership system that will officially recognize same-sex relationships.

It will begin issuing certificates to couples starting Nov. 1.

When Otsuka first found out about Tokyo’s new partnership system, he thought it would bring them few benefits. It does not offer the same legal benefits as marriage.

But when he read the metropolitan government’s explanation of who can apply under the system, something caught his eyes: Couples who chose to adopt their partner can apply.

The government must be thinking about people like them, he thought.

So, he and Shinji applied for partner status together on Oct. 14.

While the partnership is still a far cry from legalizing gay marriage, Otsuka said he feels it represents hope that marriage may be possible down the road.

“This system is a step toward same-sex marriage,” he said. “The only way to achieve same-sex marriage is to demonstrate that many people are using the partnership system.”

While similar partnership systems already exist in Japan, only around 10 percent of local governments across the country have one in place. But they now cover more than half of Japan’s population.

Tokyo’s Shibuya and Setagaya wards became the first local governments to introduce a system to recognize same-sex couples in November 2015.

According to a joint survey by the Shibuya Ward government and Nijiiro Diversity, a nonprofit organization in Osaka that advocates for rights for sexual minorities, 239 local governments, including nine prefectures, had systems like this as of Oct. 11, covering 55.6 percent of Japan’s population.

That figure will rise above 60 percent once Tokyo introduces its system.

According to the organization, 3,456 same-sex couples across the country had been officially recognized through partnership systems by the end of September.

The Tokyo metropolitan government started accepting applications on Oct. 11. By 9 a.m. on Oct. 28, 137 same-sex couples had applied.

Under these partnership systems, same-sex couples can apply for official recognition of their union by taking an oath or submitting a notarized document that proves they live together.

Under Tokyo’s system, couples can apply online by submitting their family register, a residence certificate and an identification document.

Gaining official recognition through the system allows same-sex couples to apply to move into public apartment complexes for families and apply for welfare benefits for people in the same household.

They are also allowed to visit their partners when they are hospitalized at facilities run by central or local governments, and they can give consent for doctors to operate on their ill partners.

When a member of the LGBT community applies for a mortgage, some financial institutions will regard their partner as a spouse if the couple is officially recognized by their local authority.

They will also allow the partner’s income to be added to the applicant’s income when preparing a mortgage contract.

Some insurers will allow them to receive their partner’s life insurance if they are an officially recognized couple.

Some companies will also grant them access to benefits for spouses.

But they will still be denied many privileges even if they gain partnership recognition.

That includes inheriting their partner’s assets after they die, having joint custody of children, and using the “spouse deduction” system to deduct a certain amount from a taxable income.

Same-sex couples have filed lawsuits across the nation arguing that banning same-sex marriage violates the Constitution, which guarantees “freedom of marriage.”

But judges have been split in their views so far.

While the Sapporo District Court in March ruled the ban violates the Constitution, the Osaka District Court concluded in June it does not.

Maki Muraki, head of Nijiiro Diversity, said the growing popularity of same-sex partnership systems shows a need to move toward allowing marriages as well.

“The partnership system has rapidly become widespread, which reflects how people who live with same-sex partners desperately need legal protection,” she said. “While they feel a sense of security brought by being recognized by public bodies, they also feel that the system’s legal benefits are far from that of marriage.”