Yoshitomo ordered his eldest, 15-year-old son, MINAMOTO no Yoshihira, to kill Yoshikata, who had moved to Togoku and extended influences on behalf of his father Tameyoshi in the year 1155.
久寿2年（1155年）、父の為義の意向を受けて東国に下向し勢力を伸ばしていた義賢を15歳の長男・源義平に討たせる。