上総国
Cape Hachiman was known as a natural point of maritime defense at least as early as the Heian period. The ruins of Katsuura Castle are located prominently on the cape. The castle was built in the 10th century, while Cape Misaki was part of Kazusa Province. The castle is traditionally thought to be constructed by the Okiyo no Ōkimi clan of Kazusa Province. It was later transferred to the powerful Masaki branch of the Satomi clan of Awa Province. In 1549 the Satomi clan relinquished the castle to Toyotomi Hideyoshi, who destroyed it.