TOKYO, Sept 3 (Reuters) - Princess Mako, the eldest granddaughter of Japanese Emperor Akihito, will wed a former classmate, the Imperial Household said on Sunday, confirming a marriage that will further deplete the royal family since she must become a commoner.
The announcement was aired by public broadcaster NHK.
Mako is one of only four royal grandchildren. The other three are her younger sister, Kako, her brother, Hisahito, and Crown Prince Naruhito's daughter, Aiko.
The shrinking royal population, which mirrors the broader aging of Japanese society, has raised concerns that the prince may also be the last.
See photos of Princess Mako and her fiancé:
Princess Mako through the years
Princess Mako through the years
Princess Mako, the elder daughter of Prince Akishino and Princess Kiko, speaks to media with her fiancee Kei Komuro, a university friend of Princess Mako, during a press conference to announce their engagement at Akasaka East Residence in Tokyo, Japan, September 3, 2017. REUTERS/Shizuo Kambayashi/Pool
Princess Mako, the elder daughter of Prince Akishino and Princess Kiko, and her fiancee Kei Komuro, a university friend of Princess Mako, smile during a press conference to announce their engagement at Akasaka East Residence in Tokyo, Japan, September 3, 2017. REUTERS/Shizuo Kambayashi/Pool TPX IMAGES OF THE DAY
Prince and Princess Akishino relax with their daughter Princess Mako (C) at their palace in Tokyo. Prince Akishino (R), brother of Crown Prince Naruhito, celebrates his 28th birthday November 30th . Photo taken 8NOV93
Japan's Prince Akishino and his wife Princess Kiko pose with their daughters Mako (L) and Kako on the Akasaka Palace grounds in Tokyo, in this picture released by the Imperial Household Agency on November 29, 2005 for distribution on November 30, 2005. The prince celebrates his 40th birthday on Wednesday. Picture taken November 1, 2005. FOR EDITORIAL USE ONLY REUTERS/Imperial Household Agency/Handout
Japan's Prince Akishino (R) and his daughters, Princess Mako (L) and Princess Kako, arrive at Aiiku hospital in Tokyo September 6, 2006 to see Princess Kiko and her newly-born baby boy. Princess Kiko gave birth on Wednesday to a baby boy, the first imperial male heir to be born in more than four decades and the answer to the prayers of conservatives keen to keep women off the ancient throne. REUTERS/Toshifumi Kitamura/Pool
Japan's Princess Mako, the first daughter of Prince Akishino and Princess Kiko, admires a wooden carving by Japanese sculptor Koun Takamura (1852-1934) titled "Sericulture nymph," undergoing restoration at an artefact repository at the Imperial Palace in Tokyo, in this handout picture taken October 8, 2011 and released by the Imperial Household Agency of Japan. Mako, a granddaughter of Emperor Akihito and Empress Michiko, celebrates her 20th birthday on October 23, 2011. REUTERS/The Imperial Household Agency of Japan/Handout (JAPAN - Tags: ROYALS ENTERTAINMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
Japan's Prince Hisahito (C) is flanked by his sisters Princess Mako (L) and Princess Kako in the Akasaka imperial estate in Tokyo in this August 14, 2012 handout photo by the Imperial Household Agency of Japan made available to Reuters on September 6, 2012. Hisahito turned six on September 6, 2012. Picture taken August 14, 2012. REUTERS/The Imperial Household Agency of Japan/Handout (JAPAN - Tags: PROFILE ROYALS) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
Japan's Prince Akishino (C) and his wife Princess Kiko (2nd R) are seated with their children Princess Mako (L-R), Prince Hisahito, and Princess Kako at the Akasaka imperial estate in Tokyo in this photo taken November 16, 2013 and released by Imperial Household Agency of Japan. Akishino, the second son of Emperor Akihito and Empress Michiko, celebrates his 48th birthday on November 30, 2013. REUTERS/Imperial Household Agency of Japan/Handout via Reuters (JAPAN - Tags: POLITICS ROYALS) ATTENTION EDITORS - FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
Princess Mako (L) and Princess Kako wave to well-wishers during the Japanese royal family's New Year public appearance at the Imperial Palace in Tokyo January 2, 2015. REUTERS/Thomas Peter (JAPAN - Tags: ROYALS ENTERTAINMENT SOCIETY POLITICS)
Japan's Princess Mako attends a concert at the National School of Music in Tegucigalpa, Honduras, December 9, 2015. REUTERS/Jorge Cabrera
Japan's Princess Mako arrives before a meeting with Paraguay's President Horacio Cartes at the presidential residence in Asuncion, Paraguay September 8, 2016. REUTERS/Jorge Adorno
Japan's Princess Mako is seen after her arrival at the Silvio Pettirossi International Airport in Luque, Paraguay September 7, 2016. REUTERS/Jorge Adorno
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Ten-year-old Hisahito is one of four heirs to the throne behind Akihito's two middle-aged sons, whose wives are in their early 50s, and Akihito's octogenarian brother, Masahito.
The engagement to Kei Komuro, who works in a Tokyo law office, comes after Japanese lawmakers in June approved a bill to allow Akihito to step down, the first abdication by a Japanese monarch since 1817.
A year ago, the first emperor not to be considered divine said in a rare public appearance that he feared age would make it hard to fulfill his duties. The 83-year-old has had heart surgery and been treated for prostate cancer.
But the legislation, which only applies to Akihito and not future emperors, makes no reference to the controversial topics of whether to revise a males-only succession law or to allow women to stay in the imperial family after marriage.
Conservatives fear doing so would be a first step to letting females inherit the throne.
Mako and Komuro graduated from International Christian University. She has a master's degree from the University of Leicester and has been working as a researcher at a museum. Her fiance once served as a "Prince of the Sea" to promote tourism near Tokyo, according to media reports. (Additional reporting by Kaori Kaneko; Editing by Nick Macfie)