Crown Prince Naruhito and Crown Princess Masako left for the Netherlands on Sunday to attend the coronation of the new Dutch king.

The flight would be unremarkable except for the Crown Princess, who is taking her first official overseas trip in 11 years. The former diplomat has been undergoing treatment for a vaguely explained "stress-induced illness" since 2002, when she went to New Zealand and Australia.

Before boarding a government plane at Haneda airport in Tokyo, the Crown Prince and Princess exchanged a few words with officials of the Imperial Household Agency and the Dutch ambassador to Japan, who came to see off the Imperial pair.