Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), arrives at her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), bows to well-wishers as she attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool REFILE - CORRECTING DATE

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool REFILE - CORRECTING DATE

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), waves to well-wishers as she attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool REFILE - CORRECTING DATE TPX IMAGES OF THE DAY

Japan's Emperor Naruhito speaks during a news conference on the occasion of his birthday in Tokyo, Japan February 21, 2020. Picture taken February 21, 2020. Rodrigo Reyes Marin/Pool via REUTERS

Japan's Emperor Naruhito speaks during a news conference on the occasion of his birthday in Tokyo, Japan February 21, 2020. Picture taken February 21, 2020. Rodrigo Reyes Marin/Pool via REUTERS

Japan's Emperor Naruhito speaks during a news conference on the occasion of his birthday in Tokyo, Japan February 21, 2020. Picture taken February 21, 2020. Rodrigo Reyes Marin/Pool via REUTERS

Japan's Emperor Naruhito speaks during a news conference on the occasion of his birthday in Tokyo, Japan February 21, 2020. Picture taken February 21, 2020. Rodrigo Reyes Marin/Pool via REUTERS

Japan's Emperor Naruhito speaks during a news conference on the occasion of his birthday in Tokyo, Japan February 21, 2020. Picture taken February 21, 2020. Rodrigo Reyes Marin/Pool via REUTERS

Well-wishers take pictures of royal families during the Emperor's public appearance for New Year celebrations at the Imperial Palace in Tokyo, Japan, January 2, 2020. REUTERS/Kim Kyung-Hoon

Soccer Football - Tokyo 2020 Olympics Test Event - Emperor's Cup Final - Vissel Kobe v Kashima Antlers - National Stadium, Tokyo, Japan - January 1, 2020. General view of the stadium before the match. REUTERS/Issei Kato

Soccer Football - Tokyo 2020 Olympics Test Event - Emperor's Cup Final - Vissel Kobe v Kashima Antlers - National Stadium, Tokyo, Japan - January 1, 2020. Kashima Antlers' goalkeeper Kwoun Sun-tae during the match. REUTERS/Issei Kato TPX IMAGES OF THE DAY

Soccer Football - Tokyo 2020 Olympics Test Event - Emperor's Cup Final - Vissel Kobe v Kashima Antlers - National Stadium, Tokyo, Japan - January 1, 2020. General view of the stadium during the match. REUTERS/Issei Kato

Soccer Football - Tokyo 2020 Olympics Test Event - Emperor's Cup Final - Vissel Kobe v Kashima Antlers - National Stadium, Tokyo, Japan - January 1, 2020. Vissel Kobe's Andres Iniesta, David Villa and other teammates celebrate after winning. REUTERS/Issei Kato TPX IMAGES OF THE DAY

Pope Francis leaves after a private visit at the Imperial Palace with Japan's Emperor Naruhito in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato TPX IMAGES OF THE DAY

Pope Francis meets Japan's Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Japan's Emperor Naruhito arrives to welcome Pope Francis ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis arrives to meet Japan's Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis arrives to meet Japan's Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis meets Japan's Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Pope Francis meets Japan's Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Japan’s Emperor Naruhito welcomes Pope Francis ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Japan’s Emperor Naruhito arrives to welcome Pope Francis ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Remo Casilli

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

Pope Francis meets Japan’s Emperor Naruhito ahead of a private visit at the Imperial Palace in Tokyo, Japan, November 25, 2019. REUTERS/Issei Kato

A motorcade carrying Japan's Emperor Naruhito and Empress Masako rides during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Issei Kato

Well-wishers watch the royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

Well-wishers watch the royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

Japan's Emperor Naruhito and Empress Masako wave to well-wishers during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Kim Kyung-Hoon

A man carrying Japan's national flag walks past security guards as he attends Japan's Emperor Naruhito and Empress Masako's royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Kim Kyung-Hoon

Japan's Emperor Naruhito and Empress Masako ride in a car during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Kim Kyung-Hoon

Japan's Emperor Naruhito (not seen in the picture) and Empress Masako wave to well-wishers during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Kim Kyung-Hoon

Japan's Emperor Naruhito and Empress Masako wave to well-wishers during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Kim Kyung-Hoon

Japan's Emperor Naruhito and Empress Masako wave to well-wishers during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Kim Kyung-Hoon

Japan's Emperor Naruhito and Empress Masako wave to well-wishers during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Kim Kyung-Hoon

Japan's Emperor Naruhito and Empress Masako wave to well-wishers during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Kim Hong-Ji

Japan's Emperor Naruhito and Empress Masako ride in a car during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

Well-wishers watch the royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

A motorcade carrying Japan's Emperor Naruhito and Empress Masako rides during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan November 10, 2019. REUTERS/Issei Kato

A motorcade carrying Japan's Emperor Naruhito and Empress Masako rides during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Kim Hong-Ji

Japan's Emperor Naruhito rides in a car during the royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

Japan's Emperor Naruhito and Empress Masako ride in a car during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

Japan's Emperor Naruhito and Empress Masako ride in a car during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

Japan's Emperor Naruhito and Empress Masako ride in a car during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Issei Kato

A motorcade carrying Japan's Emperor Naruhito and Empress Masako rides during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Kim Hong-Ji

A motorcade carrying Japan's Emperor Naruhito and Empress Masako rides during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Kim Hong-Ji

Japan's Emperor Naruhito and Empress Masako ride in a car during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Kim Hong-Ji

Japan's Emperor Naruhito and Empress Masako wave to well-wishers during their royal parade to mark the enthronement of Japanese Emperor Naruhito in Tokyo, Japan, November 10, 2019. REUTERS/Kim Hong-Ji