Japan celebrated the beginning of the new imperial era of Reiwa or "beautiful harmony" on Wednesday as new Emperor Naruhito ascended the Chrysanthemum Throne a day after his father Akihito abdicated.

It is the first time in more than 200 years that a member of the world's oldest royal family has chosen to step down, and solemn rituals accompanied both Akihito's abdication and Naruhito's enthronement.

Japanese, enjoying an unprecedented 10-day holiday following Akihito's abdication, packed into Meiji Jingu shrine in central Tokyo to celebrate.

As crowds lined the path, some 30 Shinto priests wearing traditional white robes and tall black hats marched under a huge gate towards the main building to conduct a festive ceremony to “report” the new emperor's accession to his ancestors, the Shinto gods.

Naruhito officially became emperor at midnight but the transition was formalised in a ceremony today.

The ritual, off-limits to all royal women, saw 59-year-old Naruhito accept the regalia relinquished by his father a day earlier: a sacred sword and jewel as well as the seal of the state and the imperial seal.

Naruhito then delivered his first address to the nation, vowing to “act according to the Constitution” while “always turning my thoughts to the people and standing with them”.

The new emperor will make his first public appearance on Saturday when he will again address the people of Japan.

The Oxford-educated Naruhito faces the delicate balancing act of continuing his father's legacy of bringing the monarchy closer to the people while upholding the centuries-old traditions of the Chrysanthemum Throne.