The Yanagisawa clan descended from the Kai Ichijo clan belonging to the Kai-Genji (Minamoto clan) and became part of the Mukawa-shu group, one of the warrior groups in the remote Kai area based in Mukawa, in the northwestern part of Kai Province.
柳沢氏が甲斐源氏の一族である甲斐一条氏の子孫が甲斐国北西部の武川筋に土着した武川衆と呼ばれる辺境武士団であった。