(Emperor Naruhito)

Emperor Naruhito performed from Thursday evening a centuries-old Shinto thanksgiving ceremony known as the Daijosai, the last of the major succession rituals following his enthronement in May, but the state-funded secretive rite has stirred controversy for its religious aspect.

Guided by ceremonial officials bearing small torches, the 59-year-old emperor clad in a white robe, entered the Yuki Hall, part of the gigantic Daijokyu complex specially constructed on the Imperial Palace grounds for the ceremony through early Friday.

It marks the first time for the emperor to offer newly harvested rice to the Shinto sun goddess Amaterasu, the mythical ancestress of the imperial family, as well as the deities of heaven and earth. He partook of it himself to give thanks and pray for the peace and prosperity of the country.

Although the main part of the ceremony was not disclosed, a total of 510 people, including Prime Minister Shinzo Abe, lawmakers, prefectural governors and other representatives, observed the first part of the rite nearby. Empress Masako, dressed in a white layered court kimono, also paid tribute at another hall in the compound.

Scholars have said the emperor, with the help of two maidservants, places food offerings including rice, salmon, abalone and chestnut on over 30 oak leaves more than 500 times before reading out a message to the ancestral gods and deities, thanking them for a peaceful and abundant harvest and wishing the same for the country.

The emperor repeated the ritual early Friday in the adjacent Suki Hall, built for his once-in-a-lifetime event along with dozens of other temporary buildings on a 6,500-square-meter area of land. The halls will be pulled down once the rite is over.

A theory put forward by folklorist Shinobu Orikuchi (1887-1953) that the emperor unites with gods on beds prepared inside the sanctum halls drew attention when the previous ceremony was held in 1990 for former Emperor Akihito, but the Imperial Household Agency has dispelled that view.

(Empress Masako)

Security was tightened, with police standing guard and a number of security vehicles placed around the palace. About 150 people attended a rally held by a group opposed to Japan's imperial system in front of Tokyo Station near the palace, according to the organizer.

"There are so many people affected by (recent) typhoons. It's wrong that a lot of tax money has been poured into the Daijosai when we're only halfway done with rebuilding," said a participant.

"The imperial system is wrong because it makes a distinction between those born noble and not. I want people to know that some are opposed to it," said a 67-year-old freelance editor.

The 1990 Daijosai faced greater threats, with extremist groups opposed to the imperial system carrying out nearly 100 attacks across the country around the time of the ritual and the preceding "Sokuirei Seiden no gi" ceremony for proclaiming the emperor's enthronement before international guests, the equivalent of a coronation.

The emperor has taken part in a series of ceremonies after he ascended the Chrysanthemum Throne on May 1, following the abdication of his father, former Emperor Akihito.

The previous succession rites include last month's "Sokuirei Seiden no gi" enthronement ceremony as well as Sunday's parade in central Tokyo, both held as state occasions.

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IN PHOTOS: Daijosai rite by then Emperor Akihito in November 1990

The Daijosai, the first annual "Niinamesai" harvest festival performed by a new emperor after his accession to the throne, dates back at least to the seventh century, although it had a hiatus of about 220 years due to a war in 1467 and was revived in 1687.

Given the Daijosai is held in Shinto style, it has been subject to criticism for it being a violation of the constitutional principle of separation of religion and state.

The concerns were first raised at the time of the previous ceremony performed by former Emperor Akihito, the first such ritual under Japan's postwar Constitution.

An Osaka High Court ruling in 1995 said doubts remain whether government financing of Shinto-linked rituals breaches the Constitution.

Last year, Crown Prince Fumihito, the younger brother of Emperor Naruhito, questioned whether the state should finance the "highly religious event," saying he has suggested using the imperial family's private funds instead.

But the prince said his proposal was rejected by the government, which maintains the public nature of the ceremony held to mark imperial succession warrants it being state-financed.

Therefore, the government will pay for the thanksgiving ceremony from the palace-related expenses, or a budget to cover the imperial family's official duties.

The total cost of the elaborate ritual has yet to be finalized, but the construction-related fees for some 30 buildings in the East Gardens of the Imperial Palace grounds, including costs to dismantle the compound, stand at about 2.44 billion yen ($22.4 million).

In the past, the Daijosai's style varied from time to time, sometimes held in a simple hut, but was made into a massive ceremony during the Meiji Era (1868-1912), when Japan tried to play up the divinization of the emperor.

The Meiji style was compiled into the 1909 "Tokyokurei" order on the formalities of the ceremony. Although the directive was abolished after World War II, former Emperor Akihito followed the style in his Daijosai and so did Emperor Naruhito.

But many measures were also taken to adjust the ceremony to modern times and reflect the wishes of Emperor Naruhito to minimize the financial burden on the people.

The size of the Daijokyu Halls was about 20 percent smaller than the previous ones, and buildings other than the main halls were constructed with regular logs rather than the conventional unpeeled logs.

The main halls' roofs were also switched from thatch material to shingle one to cut costs and reduce the time needed for construction. The timber used in the Daijokyu Halls will be recycled after the ceremony as much as possible.

In the ceremony, rice especially cultivated for the rite in the country's east and west -- Tochigi and Kyoto prefectures -- was prepared at the Yuki and Suki halls, respectively. The locations for special rice cultivation were determined by divination using turtle shells.

"I'm confident that tasty rice was produced," said 55-year-old Takeo Ishitsuka, the producer of the Tochigi rice who was among those invited to the ceremony.

"It's not something I can participate in often, so I want to engrave it in my mind," said Hisao Nakagawa, 75, who produced the Kyoto rice.

Rice and millet as well as fruits, vegetables and seafood were delivered from each of Japan's 47 prefectures, while special hemp fabric from Tokushima Prefecture and silk cloth from Aichi Prefecture were also provided.

Out of concerns over the principle of separation of state and religion, the Imperial Household Agency purchased the food and other items rather than accepting them as tributes.

In order to reduce waste, the agency also decided to consume the food, not following a tradition of burying it underground after the ceremony.

(People attend a rally held by a group opposed to Japan's imperial system.)