Miko (Imperial Prince) (皇子)

Miko, also referred to as Oji is the naming of the sons of Kotei or Tenno (emperor). The naming varies between countries, such as "Shino"(Imperial Prince), "Guno" (a second highest rank of the court rank in ancient China), "O"(King), and "Taiko"(monarchs of the European minor countries). Meanwhile, the daughters of the emperors are named Himemiko (imperial princess).

Japan
Originally, 'Miko' was used widely referring to the children and younger brothers of Gozoku (local ruling family) in the period of the Yamato sovereignty (the ancient Japan sovereignty). However, it gradually came to refer to the children and younger brothers of Okimi (great king) of the Yamato sovereignty, and upon the establishment of the emperor, 皇子, the character of Miko, started to be used for the naming.
According to Nihonshoki (Chronicles of Japan), it seems to be one of the reasons why Soga no Emishi was executed on the occasion of the Taika Reforms (Great Reformation of the Taika era) that he was conceited to make his children called with the honorific naming 'Miko.'

Yet, Miko and Himemiko became no longer used as the naming of specific imperial children, once Shino and Naishino (imperial princess) became established as the appellation for the children of the emperors. But it remained as customs to generally call the emperors' sons Miko, and then the naming became often used to refer to their relationship with the emperors such as the first Miko, the second Miko, or the first Himemiko.

Although Miko is not used as a general term at present, there are some cases to use the naming of Miko here and there, such as the Miko room to refer to the room for the children of the emperor at the Imperial Palace.

China

Europe

Aum Shinrikyo
Aum Shinrikyo bestowed on the sons of Shoko ASAHARA the title of Koshi (imperial son), as a rank of Aum Shinrikyo.