In the 8th year of the Eiroku era (1565), the Sango trio and Matsunaga Hidetoshi killed the shogun Ashikaga Yoshihide, and his younger brother Ashikaga Yoshiaki fled and hid in the house of Rokkaku. The Sanko trio lured Yoshiharu with the offer of the position of chief, and Yoshiharu agreed to do so, so Yoshiaki was exiled. Ashikaga Yoshiaki, who was exiled to the Oda family, became the best excuse for Oda Nobunaga to launch a raid on the Rokkaku family and to go to Shangluo.

After that, in order to solve the crisis of the Rokkaku family's control over the territories after the further loss of the war with the Asai clan, Rokkaku Yoshiharu formulated and enacted a very famous law of division of the daimyo of the Warring States, the Rokkaku Clan Style, in the 10th year of the Eiroku era (1567). The Shimei was a petition in which Seizen, Yoshiharu and his father, along with twenty powerful retainers, swore to abide by the law. The Rokkaku Shimei, unlike the other kokugo of the same era, was in essence a pact between the head of the Rokkaku family and the retainers to control each other's power, and the rights of the retainers were strongly guaranteed. Although Yoshiharu tried to salvage people's hearts in this way, it did not work very well.