Yūki

The Yūki were a Shimōsa warrior house claiming Fujiwara no Hidesato's blood through the Oyama family. Their founder Oyama Tomomitsu, whom family legend calls an unacknowledged son of Minamoto no Yoritomo, joined Yoritomo's rising and was enfeoffed with Yūki district in Shimōsa.

In the Nanboku-chō wars the Shirakawa Yūki served the Southern Court, while the main line followed the Northern Court. Sheltering Ashikaga Mochiuji's orphans brought the shogunate's army down on them in the Yūki War of the 1440s; the house was briefly extinguished, then revived. Masatomo and his son Masakatsu built it into a Sengoku daimyō house, and Masakatsu issued the Yūki family code in 1556.

Lacking an heir, Harutomo adopted Tokugawa Ieyasu's son Hideyasu. After Sekigahara Hideyasu was moved to Echizen and took the Matsudaira name; the Shirakawa branch had already been destroyed by Toyotomi Hideyoshi.