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Masamoto did not have his own child and originally had decided to let Hosokawa Sumiyuki, who was from Kujyō clan, succeed the house. However, he changed his mind later and decided to let Sumimoto, who was adopted after Sumiyuki, succeed the house. This naturally caused a rift between Sumimoto and Sumiyuki.
Following this, a powerful vassal under the Hosokawa, known as Miyoshi Yukinaga (Nagateru), raised troops in Settsu and destroyed Sumiyuki in the young Sumimoto's name. Kicking back Sumiyuki, Sumimoto succeeded the house in a proper form.
He and Hosokawa Takakuni, who was from a branch of Hosokawa clan and also another foster son of Masamoto, supported Ashikaga Yoshizumi, who was backed up to the 11th Shogun by Masamoto. In 1493, Masamoto had deposed the 10th Shogun Ashikaga Yoshiki (Yoshitane), who later escaped from confinement and fled to eastern countries, looking for a chance to regain his position.
In 1508, Ōuchi Yoshioki, who then harbored Yoshiki, marched his armies into Kyoto and made Yoshiki back into the seat of Shogun. The relationship between Sumimoto and Takakuni was no longer in harmony, and while Takakuni acted in concert with Yoshioki, Sumimoto was purged to Ōmi Province. Sumimoto intended to battle against Yoshioki in the province of Settsu, but ended up fleeing to Awa after seeing the superior numbers of Yoshioki's army.
Ōuchi Yoshioki left the capital in 1518 to maintain his own dominion, and regarding this as a chance, Sumimoto attempted another movement to Kyoto in the next year, cooperating with Miyoshi Yukinaga. However, Yukinaga ended up being attacked and defeated by Hosokawa Takakuni and the clan of Rokkaku, who were then at the side of Ashikaga Yoshiki. Yukinaga was caught and forced to die in seppuku. Sumimoto was ill and had not advanced to Kyoto. After Yukinaga's defeat, he escaped again to his home province of Awa and died soon.