By the middle of the 5th century an altar had appeared set atop a boulder, with a large stone in the center, surrounded by pebbles arranged in a square conguration.
Offerings of flat iron ingots that the Yamato court procured from the Korean peninsula also reflect something about the nature of overseas exchange at that time.
From the second half of the 5th century onward, rituals were performed in the shadows of boulders. Offerings from this period include iron weapons, miniature knives and axes, and highly ornamented gilt-bronze harnesses.
These objects were crafted using advanced technologies from the Korean peninsula at that time. In particular, a gold ring that bears a striking resemblance to those found in the royal Silla tombs is an important piece of evidence for the active exchanges that were taking place at this time.
Shards of Persian glass have also been discovered on the island, presumably brought to Japan by way of the distant Silk Road.
Those who engaged in dangerous ocean voyages laid out these treasures on the ground beside boulders as offerings to the gods.
During this period the Sui unified the long-divided Chinese continent; the Tang then replaced the Sui and grew increasingly powerful.
The Yamato court sent envoys to cultivate relations with the Sui and Tang rulers.
After the Tang toppled Baekje, which had long been allied with Yamato, however, Yamato sent in troops and suffered a huge defeat by Tang-Silla allied forces in 666.
After the loss, Yamato accelerated its efforts to establish a centralized government modeled on the Tang.
In the early 7th century, as the period characterized by rituals performed in the shadows of boulders came to an end, offerings shifted from items resembling burial objects found in mounded tombs to gilt-bronze miniature spinning and weaving tools, human figurines, and other objects.
In the late 7th century, rituals were performed only partly in the shadows of boulders, but mostly out in the open.
Artifacts crafted especially for these rituals include gilt-bronze miniature spinning and weaving tools and pentachords, pottery, and other items.
Written records of ancient rituals in Japan appear only from the 8th century onward, so the ritual sites on Okinoshima are an essential source of information about the formative stages of indigenous faith in Japan.
Rituals in Okinoshima appear to have changed with the times.
The ritual style that confirmed in this period became the basis of indigenous Japanese ritual practices that still survive today.
These gilt-bronze artifacts resemble the divine treasures still in use today at Ise Shrine.
In the 8th century rituals began to be performed in flat, open areas, some distance away from the group of boulders where they had been performed unil that time.
The remains of a stone altar with a large rock at its center were discovered, with an abundance of votive offersings deposited in the surrounding area.
Rituals were performed continuously on this site for about 200 years, until the end of the 9th century.
Offerings consisted mainly of a wide variety of pottery and steatite objects in the shapes of people, horses, and ships.
While these offerings share some common features with those associated with the new ritual style that prevailed at that time in Japan, some ritual objects—such as those made of pottery perforated with holes—are characterized by shapes and materials unique to the Munakata region.
Rituals with a local flavor were performed within the new framework of the state.