The history of the concept of "illegitimacy" in Japan

Japan had no equivalent to the English word bastard until the Meiji Restoration in 1868. Only then did Japanese reformers adopt Western distinctions between legitimate and illegitimate children. Prior to that time, the language had a word to indicate that a child had been born to a concubine rather than a wife, but such a child was not necessarily denied inheritance rights or legal recognition. Indeed, the Taishou Emperor, who ascended to the throne in 1912, was the son of a concubine of the last Meiji emperor.

- Stephanie Coontz, Marriage, a History