Crown Prince Fumihito, the younger brother of Emperor Naruhito, said on the occasion of his 58th birthday Thursday that a review of official duties is needed as imperial family members age or leave the royal house.

"It would be difficult to pass on (official duties) if the number (of imperial family members) decreases," the crown prince told journalists in Tokyo earlier this week.

Japanese Crown Prince Fumihito speaks to journalists at the Akasaka Estate in Tokyo on Nov. 27, 2023, ahead of his 58th birthday on Nov. 30, 2023. (Pool photo)(Kyodo)

The Japanese imperial family has been shrinking as female members are required to give up their royal status upon marrying commoners under the 1947 Imperial House Law. The current total stands at 17, with 12 being women.

As to roles as a patron or honorary patron of various associations and organizations that imperial members assume, the crown prince said, "Regarding those specialized in certain fields, imperial family members should not take on roles unless they are interested" in those particular areas.

Asked about notable events of the past year, the crown prince lamented Russia's invasion of Ukraine and the conflict between the Palestinian militant group Hamas and Israel in Gaza.

"My heart ached in the extreme" after many children fell victim during the war in Gaza, the crown prince said.

One positive the crown prince highlighted was the fact people in Japan can again interact face to face following the downgrade of the legal status of COVID-19 to the same as seasonal influenza in May.

He also said he was delighted by the achievements of Japanese shogi prodigy Sota Fujii and two-way baseball star Shohei Ohtani.

Fujii in October became the first player to simultaneously hold all eight major titles in the traditional board game, while in the same month Ohtani became the first Japanese to win an MLB home run title, adding to his many other achievements.

Regarding his family, the crown prince explained why his younger daughter Princess Kako did not move into the renovated residence in Tokyo's Akasaka Estate and instead continues to live in a separate building on the same grounds that was built as the family's temporary home.

Since the 28-year-old Princess Kako will leave the imperial family if she marries a commoner, the crown prince said he "had not intended to make a room at the residence (for her) from the start."

"As it is a private matter and due to the security aspect, we did not make it public," the crown prince said.

Although the agency had said the family, including Princess Kako, planned to move into the refurbished residence in March, it was not until June that it announced the princess' changed plan.

"I had been slow and hesitant. I regret that the (announcement) was extremely delayed," the crown prince said.

On Princess Kako's marriage, the crown prince said, "If she talks about it to us, we will closely listen to her and tell her our thinking," but added there is "nothing in particular" that he and Princess Kako are discussing on the topic.

The crown prince's eldest son, Prince Hisahito, who is second in line to the imperial throne, will turn 18 in September next year.

On his future, including enrollment to university, the crown prince said, "The most important thing is what he wants to do. I think it is good if he goes to a place where he can do that."

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