Fudai daimyō (譜代大名) was a class of daimyō (大名) in the Tokugawa Shogunate (徳川幕府) of Japan who were hereditary vassals of the Tokugawa before the Battle of Sekigahara. Fudai daimyō and their descendants filled the ranks of the Tokugawa administration in opposition to the tozama daimyō and held most of the power in Japan during the Edo period.
Shimabara Domain (島原藩, Shimabara-han) was a Japanese domain of the Edo period. Originally known as Hinoe Domain, its administrative center was initially established at Hinoe Castle in Minamishimabara, Nagasaki Prefecture. However, it was later relocated to Shimabara Castle in Shimabara, Nagasaki Prefecture. The domain was governed by various fudai daimyō clans, including the Koriki clan and the Fukōzu-Matsudaira clan.
Tozama daimyō (外様大名, "outside daimyō") was a class of powerful magnates or daimyō (大名) considered to be outsiders by the ruler of Japan during the Edo period (江戸時代). Tozama daimyō were classified in the Tokugawa shogunate (江戸幕府) as daimyō who became hereditary vassals of the Tokugawa after the Battle of Sekigahara (関ヶ原の戦い). Tozama daimyō were discriminated against by the Tokugawa and opposed to the fudai daimyō, who were allies or vassals of Tokugawa before Sekigahara.
The Rōjū (老中), usually translated as Elder, was one of the highest-ranking government posts under the Tokugawa shogunate of Edo period Japan. The term refers either to individual Elders, or to the Council of Elders as a whole; under the first two shōguns, there were only two Rōjū. The number was then increased to five, and later reduced to four. The Rōjū were usually appointed from the ranks of the fudai daimyōs with domains of between 25,000 and 50,000 koku.