Princess Mako, the first grandchild of Japanese Emperor Akihito, on Wednesday left Tokyo's Haneda airport for a nine-day official visit to Bhutan, during which she is expected to meet with King Jigme Khesar Namgyel Wangchuck.

It is the third official visit abroad by the 25-year-old princess, who will soon become engaged to a man she met at university who now works as a paralegal at a Tokyo law firm.

The princess, the eldest daughter of Prince Akishino and Princess Kiko, is set to arrive in Bhutan on Thursday after spending a night in Singapore.

She is expected to attend a welcome ceremony in the country's capital Thimpu on Friday and have an audience with the king and his wife, Queen Jetsun Pema.

On the weekend, she is scheduled to meet Japan Overseas Cooperation Volunteers and attend a flower exhibition, which was proposed by the king.

The princess will then travel to the western city of Paro, where she will visit a memorial hall set up in honor of late Japanese agriculture expert Keiji Nishioka, who helped improve vegetable farming techniques in the Himalayan country.

Before returning to Japan on June 8, she will visit Taktsang Lhakhang, an iconic Tibetan Bhuddhist temple clinging to a cliff at an altitude of 3,000 meters.

On her previous official visits, Princess Mako traveled to El Salvador and Honduras in December 2015 and Paraguay in September 2016.