Denmark's Crown Prince Frederik, left, is greeted by Japan's Emperor Akihito, center, and Empress Michiko upon arriving for a dinner at the residential building in the Imperial Palace in Tokyo Monday, June 13, 2011.

Emperor Akihito and Empress Michiko had lunch on Tuesday with Hereditary Grand Duke Guillaume of Luxembourg at the Imperial Palace in Tokyo, according to the Imperial Household Agency.

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Japanese Emperor Akihito (L) and Empress Michiko (R) greet US Secretary of State Hillary Clinton prior to tea at the Imperial Palace Residence in Tokyo, April 17, 2011.

Japanese Crown Prince Naruhito (R) and Crown Princess Masako (L) greet well-wishers gathered at the Imperial Palace in Tokyo on January 2, 2011 for the emperor's annual New Year's greetings.

In this picture released by the Imperial Household Agency on January 1, 2011, Crown Princess Masako, Crown Prince Naruhito, Emperor Akihito, Empress Michiko, Prince Akishino, Prince Hisahito, Princess Kiko (L-R in front row) and Princess Mako, Aiko and Kako (L-R in back row) pose for the annual official photo session for the new year at the Imperial Palace in Tokyo in this December 14, 2010 picture.

Japan's Emperor Akihito (C) appears with Empress Michiko (R), Crown Prince Naruhito (L) and Crown Princess Masako to well-wishers gathered to celebrate the monarch's 77th birthday at the Imperial Palace in Tokyo December 23, 2010.

Emperor Akihito delivers a speech while Empress Michiko listens during the ceremony to celebrates 120th anniversary of Japanese parliament launch at the upper house on November 29, 2010 in Tokyo, Japan. The first Japanese Parliament was held in 1890.

Empress Michiko of Japan (R) and Princess Chulabhorn of Thailand (L) shake hands at the Imperial Palace in Tokyo on Nov. 17, 2010. Looking on is Japanese Emperor Akihito. The imperial couple had dinner with the princess, who was visiting Japan to attend a conference.

Monaco's Prince Albert II (2nd L) and his fiancee Charlene Wittstock (L) are greeted by Japan's Emperor Akihito (2nd R) and Empress Michiko upon their arrival for a luncheon at the Imperial Palace in Tokyo November 1, 2010.

Japan's Empress Michiko poses for a photograph at the Imperial Palace in Tokyo October 1, 2010 in this handout photo released by the Imperial Household Agency of Japan. Empress Michiko celebrates her 76th birthday on October 20, 2010. Picture taken October 1, 2010.

Emperor Akihito and Empress Michiko attend a ceremony marking the 125th anniversary of the founding of the patent system in Japan to protect industrial property rights at a Tokyo hotel on Oct. 18, 2010.

Thai Princess Maha Chakri Sirindhorn (L) as she is greeted by Japanese Emperor Akihito (C) and Empress Michiko (R) at the Imperial residence in Tokyo on October 12, 2010.

Dutch Crown Prince Willem Alexander (L) is welcomed by Japanese Emperor Akihito (C) and Empress Michiko (R)

upon his arrival at the Imperial Palace for a dinner in Tokyo, September 13, 2010. Crown Prince Willem Alexander has visited Japan a total of 11 times, according to the Imperial Household Agency.