Emperor Naruhito is to perform a key ritual of the "Daijosai," or Great Thanksgiving Ceremony, at the Imperial Palace from Thursday evening through early Friday. The rite is for the Emperor to pray for peace and abundant harvests.
The Daijosai is considered an important event held only once in the Emperor's reign, upon his accession to the throne.
The key ritual, "Daijokyu-no-gi," is to be staged in a complex specially built for the occasion in the East Gardens of the palace grounds.
The rite starts when the Emperor enters the Yuki Hall, one of the two main structures in the complex, at 6:30 p.m. on Thursday.
He will offer newly harvested rice and other food to Amaterasu-omikami, or the Sun Goddess, and other deities. The rice is from a paddy in Tochigi Prefecture in the eastern region, chosen in a ritual in May.
The Emperor is to bow and read out a text in old Japanese, expressing gratitude for the deities and praying for peace for the state and its people, and for abundant harvests. Then he is to taste the rice and other food himself.
Then 30 minutes after midnight, the Emperor is to enter the Suki Hall, the other main structure.
He will again offer to the deities newly harvested rice, from a paddy chosen for the occasion in Kyoto Prefecture, in the western region, and other food.
He will eat them himself, and pray for peace and rich harvests.
This ritual is expected to end around 3 a.m. on Friday after the Emperor comes out of the Suki Hall.
More than 500 people, including Prime Minister Shinzo Abe, are expected to attend the ceremony. Other participants include the heads of the legislature and judiciary, Cabinet ministers, prefectural governors and representatives of various circles.
They are to stay in two structures in the complex, away from the Yuki and Suki halls.