Emperor Akihito and Empress Michiko met with Belgian King Philippe and Queen Mathilde at the Imperial Palace in Tokyo on Tuesday, the Imperial Household Agency said.
"I remember a series of impressive exchanges in friendship with the Belgian royal family," Emperor Akihito told King Philippe. The king replied he was moved by Japan's warm welcome.
A ceremony was held earlier in the day at the Imperial Palace to welcome the king and queen, who are visiting Japan as state guests to commemorate the 150th anniversary of bilateral ties.
In addition to the Emperor and Empress, the ceremony was attended by Prime Minister Shinzo Abe and his wife, Akie.
Other participants included Crown Prince Naruhito and Crown Princess Masako, in their first attendance of such an event since October 2014, when Dutch King Willem-Alexander and Queen Maxima paid a visit.
It is still rare for the Crown Princess to make public appearances as she has been receiving treatment for a stress-induced illness for over a decade.
The Imperial family and the Belgium royal family have deepened their friendship ever since the Emperor met with King Baudouin I during his trip to Europe and the United States in 1953 as crown prince. The Imperial Couple attended the funeral of the king in 1993.
During their six-day stay in Japan through Saturday, the king and queen of Belgium are scheduled to visit Yuki, Ibaraki Prefecture, accompanied by the Emperor and Empress, to see a demonstration Wednesday of local fabric weaving. They will also attend a concert Thursday.