Japan's Emperor Akihito arrives at the tomb of his late father Hirohito to report his abdication at the Musashino Imperial Mausoleum in Tokyo, Japan April 23, 2019. Koji Sasahara/Pool via REUTERS 

Japan's Emperor Akihito offers prayers to the tomb of his late father Hirohito to report his abdication at the Musashino Imperial Mausoleum in Tokyo, Japan April 23, 2019. Koji Sasahara/Pool via REUTERS 

Japan's Empress Michiko is led by a Shinto priest as she visits the tomb of late Emperor Hirohito at the Musashino Imperial Mausoleum in Tokyo, Japan April 23, 2019. Koji Sasahara/Pool via REUTERS 

Japan's Emperor Akihito arrives at the tomb of his late father Hirohito to report his abdication at the Musashino Imperial Mausoleum in Tokyo, Japan April 23, 2019. Koji Sasahara/Pool via REUTERS 

Japan's Emperor Akihito is led by a Shinto priest after visiting the tomb of his late father Hirohito to report his abdication at the Musashino Imperial Mausoleum in Tokyo, Japan April 23, 2019. Koji Sasahara/Pool via REUTERS 

An anti-Japan protester wears a mask depicting late Japanese Emperor Hirohito during a protest on the day of anniversary of Japan's World War Two surrender, in Taipei, Taiwan August 15, 2017. The word on the mask reads "Guilt". REUTERS/Tyrone Siu 

Japan's Emperor Akihito (L), flanked by Empress Michiko, waves to well-wishers who gathered at the Imperial Palace to celebrate his 83rd birthday at the Imperial Palace in Tokyo, Japan, December 23, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito delivers a speech to well-wishers who gathered at the Imperial Palace to celebrate his 83rd birthday at the Imperial Palace in Tokyo, Japan, December 23, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito waves to well-wishers who gathered at the Imperial Palace to celebrate his 83rd birthday at the Imperial Palace in Tokyo, Japan, December 23, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (2nd L) appears with Empress Michiko (R), Crown Prince Naruhito (L) and Crown Princess Masako before well-wishers who gathered to celebrate the monarch's 83rd birthday at the Imperial Palace in Tokyo, Japan, December 23, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (L), flanked by Empress Michiko, is seen through a Japanese national flag as he waves to well-wishers who gathered at the Imperial Palace to mark his 83rd birthday in Tokyo, Japan, December 23, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (3rd L), flanked by other members of the royal family, waves to well-wishers who gathered to celebrate his 83rd birthday at the Imperial Palace in Tokyo, Japan, December 23, 2016. Royal family members are (L-R) Crown Princess Masako, Crown Prince Naruhito, Emperor Akihito, Empress Michiko, Prince Akishino, and his wife Princess Kiko and their children Princess Mako and Princess Kako. REUTERS/Issei Kato 

Japan's Emperor Akihito is seen through a Japanese national flag as he waves to well-wishers who gathered at the Imperial Palace to mark his 83rd birthday in Tokyo, Japan, December 23, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (L) and Empress Michiko wave to well-wishers who gathered at the Imperial Palace to mark his 83rd birthday in Tokyo, Japan, December 23, 2016. REUTERS/Issei Kato TPX IMAGES OF THE DAY 

A student stops to bow to a portrait of Japanese former Emperor Hirohito and Empress Kojun at Tsukamoto kindergarten in Osaka, Japan, November 30, 2016. Picture taken on November 30, 2016. REUTERS/Ha Kwiyeon 

Singapore's President Tony Tan Keng Yam (L) talks with Japanese Emperor Akihito as his wife Mary Tan (R) and Empress Michiko speak during their farewell meeting at the Akasaka State Guest House in Tokyo, Japan December 2, 2016. REUTERS/Koji Sasahara/Pool 

Singapore's President Tony Tan Keng Yam talks with Japanese Emperor Akihito (R) during their farewell meeting at the Akasaka State Guest House in Tokyo, Japan December 2, 2016. REUTERS/Koji Sasahara/Pool 

Singapore's President Tony Tan Keng Yam (2nd L) and his wife Mary Chee Bee Kiang (L) listen to their national anthem with Japan's Emperor Akihito (2nd R) and Empress Michiko during the welcoming ceremony at the Imperial Palace in Tokyo, Japan, November 30, 2016. The President of Singapore is on a state visit to Japan. Crown Prince Naruhiro (rear 2nd L) and Crown Princess Masako (rear 3rd L). Japanese Prime Minister Shinzo Abe (rear 2nd R) and his wife Akie (rear R) are also seen. REUTERS/Kimimasa Mayama/ Pool 

Japan's Emperor Akihito (C), Empress Michiko (R) and Mary Chee Bee Kiang (2nd R) watch Singapore's President Tony Tan Keng Yam (L) reviewing the guard of honor during the welcoming ceremony at the Imperial Palace in Tokyo, Japan, November 30, 2016. The President of Singapore is on a state visit to Japan. Japan's Crown Prince Naruhito (rear L) and Crown Princess Masako (rear 2nd L) are seen. REUTERS/Kimimasa Mayama/ Pool 

Singapore's President Tony Tan Keng Yam (2nd L) and his wife Mary Chee Bee Kiang (L) listen to their national anthem with Japan's Emperor Akihito (2nd R) and Empress Michiko during the welcoming ceremony at the Imperial Palace in Tokyo, Japan, November 30, 2016. REUTERS/Kimimasa Mayama/ Pool 

Singapore's President Tony Tan Keng Yam (2nd L) and his wife Mary Chee Bee Kiang (L) listen to their national anthem with Japan's Emperor Akihito (C) and Empress Michiko (2nd R) during the welcoming ceremony at the Imperial Palace in Tokyo, Japan, November 30, 2016. REUTERS/Kimimasa Mayama/ Pool 

Singapore's President Tony Tan Keng Yam (R) and his wife Mary Tan (2nd L) walk with Japan's Emperor Akihito (2nd R) and Empress Michiko (C) on the red carpet during a welcoming ceremony at the Imperial Palace in Tokyo, Japan, November 30, 2016. REUTERS/Toru Yamanaka/ Pool 

Singapore's President Tony Tan Keng Yam (L) and Japan's Emperor Akihito walk together at the Imperial Palace in Tokyo in Tokyo, Japan, November 30, 2016. REUTERS/Eugene Hoshiko/ Pool 

Singapore's President Tony Tan Keng Yam (2nd L) and his wife Mary Tan (L) are greeted by Japan's Emperor Akihito (C) and Empress Michiko, upon their arrival at the Imperial Palace for their welcoming ceremony in Tokyo, Japan, November 30, 2016. REUTERS/Eugene Hoshiko/ Pool 

Singapore's President Tony Tan Keng Yam (2nd L) and his wife Mary Tan (L) are welcomed by Japan's Emperor Akihito (2nd R) and Empress Michiko upon their arrival at the Imperial Palace for their welcoming ceremony in Tokyo, Japan, November 30, 2016. REUTERS/Eugene Hoshiko/ Pool 

Singapore's President Tony Tan Keng Yam (2nd L) and his wife Mary Tan (L) are welcomed by Japan's Emperor Akihito (2nd R) and Empress Michiko upon their arrival at the Imperial Palace for their welcoming ceremony in Tokyo, Japan, November 30, 2016. REUTERS/Eugene Hoshiko/ Pool 

Shinto priests arrive for a funeral for the late Prince Mikasa, the younger brother of former Japanese Emperor Hirohito, at Toshimagaoka imperial cemetery in Tokyo, Japan, November 4, 2016. REUTERS/Koji Sasahara/Pool 

Belgium's King Philippe (2nd from L) and Queen Mathilde is guided by Japanese Emperor Akihito (2nd from R) upon their arrival at Yuki at Yuki Information + Communication Center in Yuki, Ibaraki Prefecture, north of Tokyo, Wednesday, Oct. 12, 2016. The Belgian royal couple is on a state visit to Japan. REUTERS/Shizuo Kambayashi/Pool 

Belgium's King Philippe, right, winkes for media with Japanese Emperor Akihito at Yuki Information + Communication Center in Yuki, Ibaraki Prefecture, north of Tokyo, Wednesday, Oct. 12, 2016. The Belgian royal couple is on a state visit to Japan. REUTERS/Shizuo Kambayashi/Pool 

A car carrying Belgium's King Philippe and Japanese Emperor Akihito is pictured when they leave Oyama Station in Oyama, Tochigi prefecture, for a local community center in Yuki, Ibaraki prefecture, on October 12, 2016. The Belgium's King Philippe and Queen Mathilde are here on a six-day state visit to Japan. REUTERS/Toru Yamanaka/Pool 

Belgium's King Philippe (L) and Japanese Emperor Akihito (2nd L) get on a car while Belgium's Queen Mathilde (2nd R) and Japanese Empress Michiko look on when they leave Oyama Station in Oyama, Tochigi prefecture, for a local community center in Yuki, Ibaraki prefecture, on October 12, 2016. The Belgian royal couple in on a six-day state visit to Japan. REUTERS/Toru Yamanaka/Pool 

Japan's Emperor Akihito bows during a parliament session at the Upper House after declaring the start of the new parliament session in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

Japan's Emperor Akihito arrives at the Upper House to declare the start of the new parliament session in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

Japan's Emperor Akihito declares the start of the new parliament session at the Upper House in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon TPX IMAGES OF THE DAY

Japan's Emperor Akihito declares the start of the new parliament session at the Upper House in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

Japan's Emperor Akihito leaves a parliament session at the Upper House after declaring the start of the new parliament session in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

Japan's Emperor Akihito leaves a parliament session at the Upper House after declaring the start of the new parliament session in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

Japan's Emperor Akihito attends a parliament session at the Upper House to declare the start of the new parliament session in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

Japan's Emperor Akihito (C, top) arrives at the Upper House to declare the start of the new parliament session as lawmakers and officials bow to him, in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

Japan's Emperor Akihito declares the start of the new parliament session at the Upper House in Tokyo, Japan, September 26, 2016. REUTERS/Kim Kyung-Hoon

FILE PHOTO: Japan's Emperor Akihito (R) and Empress Michiko leave after praying at the altar of late Prince Tomohito, a cousin of the Emperor, in Tokyo June 19, 2012. REUTERS/Itsuo Inouye/Pool/File Photo 

Japan's Emperor Akihito (C) and Empress Michiko (behind Akihito, R) look out at overturned ships and the damaged fishing port in Otsu town in Kitaibaraki, about 70 km (42 miles) south of the crippled Fukushima Daiichi Nuclear Power Station, April 22, 2011, during a visit to give encouragement to the survivors of the earthquake and tsunami. REUTERS/Itsuo Inouye/Pool/File photo 

Japan's Emperor Akihito waves to well-wishers who gathered to celebrate the monarch's 81st birthday at the Imperial Palace in Tokyo December 23, 2014. REUTERS/Issei Kato/File photo 

Japan's Emperor Akihito (L), flanked by Empress Michiko (2nd L), leads his royal family members Crown Prince Naruhito (4th R), Crown Princess Masako (R), Prince Akishino (behind Naruhito), Princess Kiko (behind Masako) and their daughter Princess Mako to greet guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato/File photo 

Japan's Emperor Akihito (L) and Empress Michiko (2nd L) talk with evacuees from the March 11 earthquake and tsunami, at Tokyo Budoh-kan, currently an evacuation shelter, in Tokyo March 30, 2011. REUTERS/Issei Kato/File photo 

Japan's Emperor Akihito (L) and Empress Michiko bow towards the audience as they leave the national memorial service for the victims of the March 11, 2011 earthquake and tsunami in Tokyo, Japan, March 11, 2016. REUTERS/Kazuhiro Nogi/Pool/File photo 

Japan's Emperor Akihito (R) and Empress Michiko leave after praying at the altar of late Prince Tomohito, a cousin of the Emperor, in Tokyo June 19, 2012. REUTERS/Itsuo Inouye/Pool/File photo 

Japan's Emperor Akihito (front L), flanked by Empress Michiko, greets guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Crown Princess Masako (C) talks with Japan's Emperor Akihito (in front of Masako) and Empress Michiko (behind Emperor Akihito) as she leaves an annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (front 2nd R), flanked by Empress Michiko, greets guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Empress Michiko (front R), flanked by Emperor Akihito (behind Empress Michiko), greets guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (front L), flanked by Empress Michiko, greets guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (2nd L), flanked by Empress Michiko, greets guests as guests bow to the emperor during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (L), flanked by Empress Michiko (2nd L), makes an appearance before guests with his royal family members Crown Prince Naruhito (5th R), Crown Princess Masako (4th R), Prince Akishino (3rd R), Princess Kiko (2nd R) and their daughter Princess Mako during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato TPX IMAGES OF THE DAY

Japan's Emperor Akihito (L), flanked by Empress Michiko (2nd L), makes an appearance before guests with his royal family members during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (C), flanked by Empress Michiko, leads his royal family members to greet guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (top L), flanked by Empress Michiko, makes an appearance before guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito (L), flanked by Empress Michiko (2nd L), leads his royal family members Crown Prince Naruhito (4th R), Crown Princess Masako (R), Prince Akishino (behind Naruhito), Princess Kiko (behind Masako) and their daughter Princess Mako to greet guests during the annual spring garden party at the Akasaka Palace imperial garden in Tokyo, Japan, April 27, 2016. REUTERS/Issei Kato 

Japan's Emperor Akihito, flanked by Empress Michiko, delivers an address in front of an altar for the victims of the March 11, 2011 earthquake and tsunami at the national memorial service in Tokyo, Japan, March 11, 2016. Japan on Friday mourned the thousands who lost their lives in a massive earthquake and tsunami five years ago that turned towns to matchwood and triggered the world's worst nuclear disaster since Chernobyl in 1986. REUTERS/Kazuhiro Nogi/Pool 

Japan's Emperor Akihito (L) and Empress Michiko bow towards the audience as they leave the national memorial service for the victims of the March 11, 2011 earthquake and tsunami in Tokyo, Japan, March 11, 2016. Japan on Friday mourned the thousands who lost their lives in a massive earthquake and tsunami five years ago that turned towns to matchwood and triggered the world's worst nuclear disaster since Chernobyl in 1986. REUTERS/Kazuhiro Nogi/Pool