吾妻鏡
Some articles of 1187 of the "Azuma Kagami" state that Ata Tadakage of Satsuma Province fled to sometime around 1160. The "Azuma Kagami" also states that in 1188 Minamoto no Yoritomo, who soon became the "shōgun", dispatched troops to pacify . 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 , 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 to from the end of the 12th century to the early 13th century.