tennō
The Emperor of Japan is the monarch and the head of the Imperial Family of Japan. Under the Constitution of Japan, he is defined as the symbol of the Japanese state and the unity of the Japanese people, and his position is derived from "the wi ...
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kugyō
is the collective term for the very few most powerful men attached to the court of the Emperor of Japan in pre- Meiji eras. The term generally referred to the and court officials and denoted a court rank between First Rank and Third Rank un ...
(court officials), '' shōgun'' and '' daimyōs'' often had several wives to ensure the birth of an heir. The ''seishitsu'' had a status above other wives, called ''sokushitsu'' (側室, concubine).
The system dates back to the ritsuryō system in the Nara and Heian periods. At the time, the main wife was called ''chakusai'' (嫡妻). The last Japanese emperor to have official concubines was
Emperor Meiji
, also called or , was the 122nd emperor of Japan according to the traditional order of succession. Reigning from 13 February 1867 to his death, he was the first monarch of the Empire of Japan and presided over the Meiji era. He was the figur ...
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Succession disputes between sons of the official wife and concubines were a constant source of internal, often armed conflict within houses ( O-Ie Sōdō).