Japanese Emperor Naruhito and Empress Masako had dinner with visiting Dutch King Willem-Alexander at the Imperial Palace in Tokyo on May 22.

Officials said the imperial couple's daughter Princess Aiko joined them in their after-meal chat.

The king was in Japan to attend the Netherlands' National Day activities at the Osaka Expo on May 21.

Japan's Princess Hisako of Takamado joined him in the celebrations in western Japan.

Naruhito and Willem-Alexander have had close ties for many years.

In the summer of 2006, the emperor and his family made a private trip to the Netherlands.

The two also tackled water-related issues together, including serving on the UN Secretary-General's Advisory Board on Water and Sanitation prior to their accession.

Then Crown Prince Naruhito was honorary president and then Prince of Orange Willem-Alexander was chair of the now phased-out board.