[1] Okamoto Castle was located on a hill with an elevation of 60 meters overlooking Tokyo Bay, north of the former town of Tomiura.

The minor lords of Awa were loyal to the Kanrei, but geographically the province was very near Kamakura, separated only by the narrow Uraga Channel.

In response, Satomi Yoshitoyo launched an amphibious invasion of Kamakura, in the process of which his forces burned down the famed Shinto shrine of Tsurugaoka Hachiman-gu.

The Hōjō were far stronger, and their armies broke the Satomi forces and even attacked Kururi Castle, but Yoshitaka turned to Uesugi Kenshin for assistance and kept his independence.

Yoshitaka's son, Satomi Yoshihiro (1530-1578) pledged fealty to the Hōjō and surrendered the northern half of Kazusa Province.

During an archaeological excavation, fragments of Chinese porcelain and other trade goods were discovered, indicating that the area was also used as a port.

In 1898, a monument was erected by an old pine tree on the castle site said to be a surviving remnant of a garden from the time of Satomi Yoshiyori.