The details of his identity are unknown, but his name indicates that he would have been a member of the family of FUJIWARA no Harumochi, who was one of the leaders of a rebellion in the Johei-Tengyo Disturbances and appointed as a local government officer of Hitachi Province by TAIRA no Masakado.
素性の詳細は不明で、その姓名から承平天慶の乱の首謀者の一人で平将門に常陸国国司に任ぜられている藤原玄茂の一族と考えられる。