The OIKAWA clan became a retainer of the KASAI clan, which had influence from the southern part of Iwate Prefecture to the north part of Miyagi Prefecture but, due to the consequent development, was divided into three family lines.
及川氏は岩手県南部から宮城県北部にかけて勢力を有した葛西氏の家臣となったが、その経緯から三つの家系に分かれている。