Five regent houses

The Five Regent Houses (五摂家; "go-seike" or "go-sekke") is a collective term for the five families of the Fujiwara clan. The leaders of these families monopolized the position of "Sekkan" in the Japanese Imperial Court in Kyoto between the 12th and 19th century. The five houses are Konoe, Takatsukasa, Kujō, Ichijō, and Nijō.
The Fujiwara clan also had other families, but traditionally, only these five were eligible for regentship. They were the most politically powerful families among the kuge (court officials).
The imperial clan claimed descent from the goddess Amaterasu, but in the Fujiwara tradition, the clan descended from another ancient Kami known as Ame-no-Koyane. It is said that only these two clans were left in the modern era to claim Kami descent.