A look at Japan's shrinking royal line of succession

Tokyo — Japan's imperial family is relatively small and will shrink further in the coming years.

Only one of Emperor Akihito's four grandchildren is a male who can ascend to the throne. The three princesses likely will lose their royal status eventually, since they are required to do so if they marry commoners.

READ NEXT: Unpacking the first Japanese royal abdication in 200 years

Here is a at the royal family as Akihito abdicates:

EMPRESS MICHIKO, 84

Akihito's wife, born Michiko Shoda, is the daughter of a wealthy businessman who led the Nissin Flour Milling Co. She graduated from the University of the Sacred Heart with top honours in English literature and has written and translated children's books.

Michiko met Akihito at a 1957 tennis tournament remembered as a "love match," and the couple married two years later. She was the first commoner to marry an emperor and was part of many changes Akihito brought to Japan's ancient monarchy. They broke tradition by raising their three children instead of leaving their care to palace staff. They travelled around Japan, reaching out to those with disabilities or other difficulties. When the couple met people coping with disasters, Michiko led the interactions, typically kneeling on the floor "Heisei style," named after Akihito's era.

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(Photo: Emperor Akihito and Empress Michiko in 2015. Getty Images.)

CROWN PRINCE NARUHITO, 59, AND CROWN PRINCESS MASAKO, 53

Naruhito, whose name in Chinese characters means a virtuous person, will ascend the Chrysanthemum Throne on Wednesday as the 126th emperor in a line dating to the fifth century. A historian and a viola player, Naruhito is Japan's first emperor-to-be to have studied abroad and could expand his role to global issues. He has pledged to inherit his father's devotion to peace and compassion for the people, while exploring his own style.

Naruhito married a Harvard-educated former diplomat, Masako. After graduating from Gakushuin, a private school for former aristocrats, Naruhito studied at Oxford University and authored a paper on the historical Thames River water transportation systems.

Harvard-educated Masako Owada had a promising future as a diplomat when she captured Naruhito's eye at a 1986 tea party. It took Naruhito seven years of waiting, during which Masako studied at Oxford and refused him twice. She finally accepted his proposal and the two married in 1993.

Despite growing expectations that she may help modernize and internationalize the palace, Masako has largely receded from the public since the early 2000s after giving birth to daughter Aiko and developing stress-induced depression. In 2004, Naruhito subtly criticized the heated attention and pressure placed on Masako to produce a boy while depriving her of foreign visits. Naruhito says Masako is steadily recovering and hopes to gradually expand her role.

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(Photo: Crown Prince Naruhito and Crown Princess Masako in 2018. Getty Images.)

PRINCESS AIKO, 17

The only child of Naruhito and Masako would have been next in line to the throne if born in a gender-equal nation. But Japan's Imperial House Law only allows males to rule. As a child, Aiko enjoyed watching sumo and memorised wrestlers' names and ranks. Having parents who studied in Britain, Aiko has participated in a summer program at Eton College.

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(Photo: Crown Prince Naruhito, Crown Princess Masako and their daughter Princess Aiko in 2010. Getty Images)

PRINCE FUMIHITO, 53, AND PRINCESS KIKO, 52

The younger of Akihito's two sons, Fumihito is better known as Akishino, his childhood title, and will be crown prince during Naruhito's reign. His future stint will be short, if at all, and there is speculation that Fumihito may skip his turn and hand it to his 12-year-old son, Prince Hisahito. Affectionately known as prince "catfish," his research subject, Fumihito has visited Thailand a number of times to study fisheries and the domestication of chickens.

He met his future wife, Kiko, at Gakushuin University, where both were students. Contrary to his brother's attentive team-player image, Fumihito is said to be free-spirited and outspoken, at times critical of his elder brother. He and Kiko have two daughters and a son.

Kiko, formerly Kiko Kawashima, grew up in the US and Austria and lived in modest housing after returning to Japan. She was called the "apartment princess" when she married Fumihito in 1990. Twelve years after the couple had their second daughter, Kiko gave birth to Hisahito in 2006 amid intense attention on a possible male heir. Hisahito's birth halted a government debate on whether to change the succession rules to allow a female emperor.

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(Photo: Prince Akishino and his wife Princess Kiko in 2006. Getty Images.)

PRINCE HISAHITO, 12

The only male of Akihito's four grandchildren, Hisahito will be second in line to the throne when the new era begins, and there is nobody left after him. The male-only succession rules maintained by the government and its right-wing supporters put him on the spot, with heavy pressure to produce a male heir. Akihito's abdication reminded the government of a need to resume discussion on how to maintain the royal population and a stable succession.

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(Photo: Prince Hisahito in 2019. AP Photos.)

PRINCESS MAKO, 27

The oldest of Akihito's four grandchildren and sister of Hisahito, Mako has been a target of tabloid coverage due to her boyfriend's family debt scandal that pushed back their planned marriage to 2020 amid growing uncertainty. Her college classmate and boyfriend, Kei Komuro, is now studying law at Fordham University in New York.

READ MORE HERE: Japan princess relinquishes royal title to marry a commoner

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(Photo: Princess Mako in 2011. Getty Images)

PRINCESS KAKO, 24

The second-oldest of Akihito's grandchildren, Kako recently graduated from the International Christian University in Tokyo, where she studied psychology. She won't seek a job and is expected to take on official duties as a member of the royal family. Kako spent a year studying performing arts at Leeds University in Britain and enjoys hip-hop dancing. She has published photo books as her looks and fashion gained followers.

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(Photo: Princess Kako in 2018. Getty Images)