quality:correction, structural:expansion, information:filtering
Kikaigashima and Iōgashima

The southern islands reappeared in written history at the end of the 10th century. According to the Nihongi ryaku (c. 11th–12th centuries), Dazaifu, the administrative center of Kyushu, reported that the Nanban (southern barbarians) pirates, who were identified as Amami islanders by the Shōyūki (982–1032 for the extant portion), pillaged a wide area of Kyūshū in 997. In response, Dazaifu ordered "Kika Island" (貴駕島, Kikashima) to arrest the Nanban. This is the first attested use of Kikaigashima, which is often used in subsequent sources.

The series of reports suggest that there were groups of people with advanced sailing technology in Amami and that Dazaifu had a stronghold on Kikai Island. In fact, historians hypothesize that the Amami Islands were incorporated into a trade network that connected it to Kyūshū, Song China and Goryeo. In fact, the Shōyūki recorded that in the 1020s, local governors of southern Kyūshū presented to the author, a court aristocrat, local specialties of the southern islands including the Chinese fan palm, redwoods, and shells of Green Turban Shell. The Shinsarugakuki, a fictional work written in the mid-11th century, introduced a merchant named Hachirō-mauto, who traveled all the way to the land of the Fushū in the east and to Kika Island (貴賀之島, Kikanoshima) in the west. The goods he obtained from the southern islands included shells of Green Turban Shell and sulfur. The Shinsarugakuki was not mere fiction; the Golden Hall of Chūson-ji (c. 1124) in northeastern Japan was decorated with tens of thousands of green turban shells.

Some articles of 1187 of the Azuma Kagami state that Ata Tadakage of Satsuma Province fled to Kikai Island (貴海島, Kikaishima) sometime around 1160. The Azuma Kagami also states that in 1188 Minamoto no Yoritomo, who soon became the shōgun, dispatched troops to pacify Kikai Island (貴賀井島, Kikaishima). It was noted that the imperial court objected the military expedition claiming that it was beyond Japan's administration. The Tale of the Heike (13th century) depicted Kikai Island (鬼界島, Kikaishima), where Shunkan, Taira no Yasuyori, and Fujiwara no Naritsune were exiled following the Shishigatani Incident of 1177. The island depicted, characterized by sulfur, is identified as Iōjima of the Ōsumi Islands, which is part of Kikai Caldera. Since China's invention of gunpowder made sulfur Japan's major export, Sulfur Island or Iōgashima became another representative of the southern islands. It is noted by scholars that the character representing the first syllable of Kikai changed from ki (貴, noble) to ki (鬼, ogre) from the end of the 12th century to the early 13th century.

The literature-based theory that Kikai Island was Japan's trade center of the southern islands is supported by the discovery of the Gusuku Site Complex in 2006. The group of archaeological sites on the plateau of Kikai Island is one of the largest sites of the era. It lasted from 9th to 13th centuries and at its height from the second half of the 11th to the first half of the 12th century. It was characterized by a near-total absence of the native Kaneku Type pottery, which prevailed in coastal communities. What were found instead were goods imported from mainland Japan, China and Korea. Also found was the Kamuiyaki pottery, which was produced in Tokunoshima from the 11th to 14th centuries. The skewed distribution of Kamuiyaki peaked at Kikai and Tokunoshima suggests that the purpose of Kamuiyaki production was to serve it to Kikai.