Japanese Emperor Naruhito pledged to fulfil his duty as he officially announced his enthronement on Tuesday in a ceremony attended by dignitaries from more than 180 countries.
Naruhito, 59, proclaimed his enthronement to the world in a ceremony called Sokuirei-Seiden-no-gi at the Imperial Palace in Tokyo before 2,000 guests.
In the 30-minute ceremony, which has been performed for centuries, Japan's 126th emperor promised to "fulfil my responsibility as the symbol of the state and of the unity of the people". His wife, Empress Masako, sat beside him.
The ceremony was attended by dignitaries including Sheikh Hazza bin Zayed, Deputy Chairman of Abu Dhabi Executive Council, and Britain's Prince Charles.
Naruhito acceded to the throne in May after his father, Akihito, became the first monarch to abdicate in two centuries.
The enthronement ceremony is one of several celebrations for Naruhito, who has been a full-fledged emperor since succeeding his father in May.
He wore a formal ochre-coloured robe that had been dyed in sappanwood and Japanese wax tree bark, and a black headdress decorated with an upright tail, as his father did 30 years ago, in a ceremony at the Imperial Palace's most prestigious hall.
Naruhito made his proclamation from the Imperial Throne Takamikura, a 6.5-metre tall decorative structure resembling a gazebo.
"I sincerely hope that Japan will develop further and contribute to the friendship and peace of the international community, and to the welfare and prosperity of human beings through the people's wisdom and ceaseless efforts," he said.
The enthronement will be followed by a three-hour banquet on Tuesday evening, which world leaders will attend.
Foreign guests will be escorted to observe the Imperial Throne and the Empress' seat on display at the Pine Hall before entering the banquet hall, where a dinner will be served while traditional Japanese court music is performed, ceremony organisers said.
Emperor Naruhito's grandfather, Hirohito, in whose name Japanese troops fought the Second World War, was treated as a god but renounced his divine status after Japan's defeat in 1945. Emperors now have no political authority.
Long-planned celebrations, for which Japan declared a national holiday, were tempered after Typhoon Hagibis, which killed at least 82 people, tore through Japan 10 days ago.
A public parade was postponed until next month to allow the government to devote attention to the typhoon clean-up, while Tuesday's pouring rain forced the palace to scale back the number of courtiers in ancient robes.
But just before the ceremony began, the skies cleared and a rainbow appeared over Tokyo.
Prime Minister Shinzo Abe delivered a congratulatory speech before assembled dignitaries including Crown Prince Akishino, the emperor's younger brother, and his family, all adorned in brightly coloured robes.
Other guests included US Transport Secretary Elaine Chao and Myanmar civilian leader Aung San Suu Kyi.
Mr Abe led a trio of cheers of "banzai", or "long life", for the emperor, before a 21-gun salute.