According to the Kojiki, the "Records of Ancient Matters" complied in 712, the Oki Islands were the third of the islands created by the deities Izanagi and Izanami, after Awaji Island and Shikoku Island; they were recorded under the name Oki-no-mitsugo-no-shima (the "Oki triplet islands"), or alternatively Ame-no-oshikorowake. Also, according to the Nihon Shoki, the "Chronicles of Japan" compiled in 720, Oki and Sado Island were born as twins.
The fact that the Oki Islands were treated extensively in these documents suggests that the imperial court at the time considered these islands as quite important, and one of these reasons is believed to be obsidian. Obsidian mined in the Oki Islands was mainly circulated in the Chūgoku region from 30,000 years ago. People and culture interacted through the obsidian trade, and it can be seen that the Oki Islands prospered from prehistoric times to ancient times.