Isumi

In the sixteenth century, the Kazusa Toki family ruled the Isumi district from Mangi Castle. They patronised temples including Gyōganji, Izunadera and Kiyomizudera, while fighting the Satomi of Awa, the Masaki of Odaki and the Takeda of Chōnan. Their association with the Later Hōjō brought their downfall in Toyotomi Hideyoshi's campaign of 1590.

Under the new Tokugawa order, development of rice land reshaped the district. Honda Tadatomo, lord of Ōtaki, promoted reclamation at Kuniyoshihara in 1609 and Mangihara in 1611, offering temporary exemptions from taxes and other obligations to encourage the work. Isumi also sustained intellectual connections: Usami Shinsui studied under Ogyū Sorai, while his pupil Nakamura Kunika compiled the regional history Bōsō Shiryō. Warrior strongholds, newly opened fields and local scholarship thus marked successive phases of Isumi's early modern life.