Yonaguni Island is the southwesternmost boundary of Japan. On clear summer days, it is possible to view mountains of Taiwan over Yonagunifs western horizon.

When visiting this island, one will get the impression of a very bright place inhabited by people of simple charm, always ready with a warm smile. However, this easy-going environment was not always the norm, especially for women about to give birth.

Outside the village of Kubura, there exists a gap in the stone surface of the ground called the Kubura Rock Cleft. It is about nine feet wide and twenty feet deep. According to legend, all pregnant women of the village had to jump over this cleft, leaving those who were unsuccessful seriously injured or dead. Even those women who cleared the gap could later suffer a miscarriage or complications leading to death caused by the jump.

Mr. Eijun Kishaba, a historian of Yaeyama, has concluded that this terrible custom was adopted by the leaders of the island as a means of population control. In the 15th century, the population of Yonaguni had expanded to over 30,000 people as a result of several years of prosperity.

This practice was later abolished through the efforts of a brave woman named Sanfai Isoba, who later became the leader of the island after defeating the former chieftains.