Isa

The Isa were a warrior family of Isa District in Hitachi Province and the kin from whom the Date clan sprang. In 1189 Isa no Tamemune, eldest son of the local lord Hitachi Nensei, won distinction at the Battle of Ishinazaka on Minamoto no Yoritomo's Ōshū campaign. Nensei received the Date and Shinobu districts in Mutsu and took the name Date, while Tamemune kept the old estate and called himself Isa.

Tamemune is said to have drowned fighting for the Kamakura shogunate in the Uji River during the Jōkyū War of 1221. When the war of the Northern and Southern Courts began, Isa Yukisuke followed Kitabatake Akiie for the Southern Court.

Yukisuke held Isa Castle with nearby garrisons until it fell in 1343. The house lost its lands and disappeared as a power, though families bearing the name later served the Yūki of Shimōsa.