Is the term used for the distinctive Ryukyuan form of castles or fortresses. The first, the capital of After the Late Shell Mound period, agriculture started about the 12th century, with the center moving from the seashore to higher places. In these islands, the presence of shell axes, 2500 years ago, suggests the influence of a southeastern-Pacific culture. Shell rings for arms made of shells obtained in the, namely and islands, were imported by Japan. In Okinawa, rice was not cultivated until the Middle Shell Mound period. In the latter part of this period, moved near the seashore, suggesting the engagement of people in fishing. The Early Shell Mound period was a society, with wave-like opening. Early Okinawan history is defined by or shell heap culture, and is divided into Early, Middle, and Late Shell Mound periods.