After Masamoto was assassinated by a chief retainer of the Sumiyuki HOSOKAWA group, he overthrew Sumiyuki and came into power by backing up Shogun Yoshizumi ASHIKAGA with Sumimoto.
政元が細川澄之派の重臣によって暗殺されると、澄之を打倒し、澄元と共に将軍・足利義澄を擁立して権勢を掌握した。