Emperor Koan (孝安天皇)

Emperor Koan (427 B.C. - February 23, 291 B.C.) was the sixth emperor (reign: February 26, 392 B.C. - February 23, 291 B.C.), being described in "Kojiki" (The Records of Ancient Matters) and "Nihonshoki" (Chronicles of Japan). In Kojiki, he is called Yamatotarashihiko kunioshihitonomikoto or Oyamatotarashihiko Kunioshihitonomikoto. He was one of the so called Kesshi-Hachidai (Eight Undocumented Sovereigns), and it is commonly understood that he was a nonexistent Emperor (there is also the theory of his existence).

Imperial Palace
The capital was Muro no akizushima no miya.
(It is present Muro, Gose City, Nara Prefecture.)

Achievements
There is no description about his achievements. In February, 408 B.C., he was formally installed as Crown Prince, and after the death of his father in 393 B.C., he ascended the throne on next New Year's Day. The period of his reign as Emperor was 102 years, which is the longest among the successive Emperors so far, however it is very much unreliable. According to Kojiki, he died at the age of 123, while according to Nihonshoki, he died at the age of 137.

Imperial mausoleum
It is said that he was buried in Tamade no okanoeno misasagi. Currently, this misasagi is identified with the round barrow, which was located in Tamade no okanoeno misasagi, Tamade, Oaza, Gose City, Nara Prefecture.