Kōshō is the fifth emperor (tenno) of Japan to appear on the traditional list of emperors. This posthumous name (if he ever lived) literally means "filial manifestation." His Imperial Majesty, Emperor Akihito of Japan The Emperor of Japan (天皇, tennō) is Japans titular head of state and the head of the Japanese imperial family. ... A posthumous name (Traditional Chinese: 諡號/謚號 Simplified Chinese: 谥号; Pinyin: shì hào; Romaji: shigō/tsuigō; Revised Romanization of Korean: siho) is a honorary name given to royalty in some cultures posthumously, that is, after the persons death. ...

Later generations have included this name to the list of emperors (tenno) of Japan (as 孝昭天皇, Kōshō Tennō), thus making him posthumously an emperor and assigning him as one of the early sovereigns and ancestors of the dynasty that has reigned unbroken since time immemorial. If he lived, at his time the title tenno was not yet used, and the polity he possibly ruled did certainly not contain all or even the most of Japan. Concluding from his alleged successors in beginnings of historical time, also Kosho would have been a chieftain, local king, in early Yamato tribal society. To meet Wikipedias quality standards, this article or section may require cleanup. ... The Yamato people (Japanese: 大和民族) are the dominant native ethnic group of Japan. ...

No firm date can be assigned to this monarch and he is regarded by historians as a "legendary emperor", a mythical figure. He was the fourth one of eight emperors without legend. In Kojiki and Nihonshoki only his name and genealogy were recorded. Kojiki or Furukotofumi (古事記) is the oldest surviving historical book dealing with the ancient history of Japan. ... Nihonshoki (日本書紀) is the second oldest history book about the ancient history of Japan. ...

His historical existence was believed traditionally and a tomb was attributed to him, but contemporary studies support the view that no such person existed.