King (of imperial family) (王 (皇族))
King (O, miko, or okimi in ancient time) is one of the positions or titles of the Imperial family. Or a member of an Imperial family who receives the position of the king.
In the Ritsuryo codes, it referred to sons of the Imperial family who were not given the title of Imperial Prince. In the present Imperial House Law, it refers to sons of the Imperial family who are in the direct line and in the three or more degree of kinship from the emperor (not in collateral line and counted from the emperor who is a direct ancestor). The wife of the king is called empress (of imperial family).
As of September, 2007, there were queens (of imperial family), but no kings in Japan.
When a king becomes an adult, he is given Grand Cordon of the Order of the Paulownia Flowers of the Rising Sun (or Grand Cordon of the Order of the Rising Sun with Paulownia Flower if he became an adult before November 2, 2003).
According to the Japan-Korea Annexation Treaty and the related imperial edict, 'His Majesty the Emperor of Korea, His Majesty the Retired Emperor, His Majesty the Crown Prince and their empresses and descendents' were called the royal family, and the head of the Lee royal family was also called a king, but the king of the imperial family was different from the king of the royal family.
Soon after Japan established diplomatic relations with the West at the end of Edo Period, the Japanese government misunderstood that the relationship between the emperor (Japanese emperor) and king of the West was an unequal relationship like that of Japan and China, and discriminated sovereign's messages to imperial states from those to royal states, causing confusions.