However, soon afterwards the domain erupted into a civil war between the two chief karō, Ogawa Shiroemon and Iori Iki.
Takebe Masanaga of neighboring Hayashida Domain unsuccessfully attempted an arbitration, and in 1640 the shogunate was forced to directly intervene, ordering the seppuku of 20 senior retainers.
Under most circumstances, this would have included Ikeda Teruzumi himself, but since he was a grandson of Tokugawa Ieyasu, he was demoted to a kokudaka of 10,000 koku and reassigned to Shikano Domain in Inaba Province.
Another cadet branch of the Ikeda clan came to Yamasaki from the Kojima sub-domain of Okayama Domain and riled to 1672, when the line went extinct due to lack of an heir.
The 8th daimyō Honda Tadachika opened the han school Shisaikan" and made an effort to rebuild the clan's finances.