In the months since then, he has emphasised both continuity with the long history of the imperial family in Japan, as well as demonstrating a more global outlook.

In his first address as emperor to the country on May 1, Naruhito vowed to "fulfil my responsibility as the symbol of the state and of the unity of the people of Japan, while always turning my thoughts to the people and standing with them."

He swore to "reflect deeply" on the course followed by his father and past emperors.

The diplomacy started soon afterwards, however. In late May, Naruhito welcomed US President Donald Trump as the first state guest since he became the 126th emperor.

In his remarks at the state banquet, the 59-year-old emperor thanked Trump for the support that Japan received from the United States in the 2011 earthquake and tsunami disaster, which also caused a triple meltdown at the Fukushima Daiichi plant.

"Before everything else, we in Japan will never forget the exceptionally warm support received from the government and people of your country" in the wake of the disaster, the emperor told the president.

Naruhito, born on February 23, 1960, became heir to the throne in January 1989 following the death of his grandfather Emperor Hirohito. He officially became crown prince in a ceremony in February 1991.

Naruhito graduated from the Department of History of Gakushuin University in Tokyo in 1982 and a year later he entered Merton College at the University of Oxford, studying there for a further three years. He also completed the first part of a doctorate in humanities at Gakushuin University's graduate school in 1988.

In 1993, the imperial palace announced his long-awaited engagement to Masako Owada, a career diplomat who graduated from Harvard University, majoring in economics. The wedding ceremony was held in June the same year.

Naruhito and Empress Masako have a 17-year-old daughter Princess Aiko, who was born in 2001. While Masako has suffered from a stress-induced adjustment disorder and undergone treatment, Naruhito, unlike many Japanese fathers, has played an active role in rearing the couple's daughter.

Dressed in casual attire, Naruhito and Masako have visited disaster-hit areas following earthquakes and the tsunami that caused the Fukushima nuclear power plant disaster in 2011 and talked to affected residents.

Naruhito is also known for his research into water issues as he has delivered various speeches at conferences around the world.

He enjoys playing tennis, jogging and mountain climbing and he also plays the viola and has performed in public.

Naruhito has also travelled to a number of countries to help foster bilateral relations, including a trip to Malaysia in 2017 on the 60th anniversary of diplomatic ties between Japan and the South-East Asian country.

Australian Associated Press