For the first time in 200 years, a Japanese emperor will abdicate from the throne

It’s official: Japanese Emperor Akihito will abdicate from the throne, making him the first Japanese monarch to do so in 200 years.

In the historic bill passed by the Japanese parliament, the 83-year-old Akihito will be allowed to leave the throne, likely by 2018. The bill emphasizes that this exception has been made only for Akihito, meaning that future emperors, such as Akihito’s eldest son Naruhito, won’t be able to use it to retire ahead of time. Like most of the emperors since the 1800s, he will likely have to rule until death.

This bill comes after the emperor made a rare televised address to the country where he strongly hinted that his declining health was making it difficult for him to continue working. Because the royal family isn’t allowed to comment on politics (a legacy from post-World War II reforms to Japan’s constitution), Akihito wasn’t able to openly ask to retire, which would’ve been seen as a comment on the law.

Nonetheless, it seems the country has heard him. Preparations are already underway for Akihito to leave the throne and hand over rulership to Crown Prince Naruhito.

To people outside Japan, it may not seem like big news that an octogenarian who has battled prostate cancer and undergone heart bypass surgery wants to retire from his job.

But to Japanese, this a really big deal, and certainly not a topic that’s going away anytime soon. That’s because issues of abdication and succession within the royal family are at the center of a debate over imperial traditions and how sustainable they are in modern Japan.

Akihito himself talked about this tension in his speech, saying he’s “always felt a deep sense of responsibility” to protect the traditions of his role, but grappled at the same time with how to adapt it to a world that is “constantly changing.”

The Japanese royal family is the oldest continuous monarchy in the world, with a lineage dating back to 600 BC. As the Japan Times explained, there have been concerns in recent years that the royal family isn’t producing enough male heirs to continue this bloodline, and Akihito’s abdication has made those concerns all the more pertinent.

Since the 1800s, Japan has not allowed female heirs to ascend the throne. In fact, imperial law dictates that when princesses choose to marry a “commoner,” as Princess Mako decided to this year, they automatically lose their royal status.

While Akihito has two sons, only one of his four grandchildren, 10-year-old Prince Hisahito, is male. This is just part of a larger gender imbalance in the royal family: of 19 family members, 14 of them are female, and six of them, in addition to Princess Mako, are single, CNN reported.

This means that even if the royal family puts aside the troubling possibility of diminishing male heirs, the family is still at risk of losing as many as six of its daughters should they choose to marry outside the imperial clan. This raises serious concerns over whether the royal family will be able to continue its public duties into the next century.

Given this wider context, Akihito’s abdication really is momentous for Japan. Not only does it break centuries of tradition, it raises some very difficult (and urgent) questions on the future of the Japanese royal family — an institution as old as the country itself.