Ashikaga Yoshimasa
His conflicts with his father-in-law, Yamana Sōzen, who resented the power Hosokawa had as Kanrei, were among those that ignited the Ōnin War in 1467. When the Shōgun Ashikaga Yoshimasa had a son in 1464, Yamana took this as an opportunity to oppose Hosokawa further, supporting the child as heir to the Shogunate. Hosokawa had always worked closely with the Shōgun's brother Ashikaga Yoshimi and supported his claim to the shogunate.