朝鮮漂流人 十五世紀的琉球 琉日國界 臥蛇島 與那國島 八重山群島 尚真王及其母 小琉球 蔡璟 Ship-wrecked Korean survivors Fifteenth century Liu-Kiu The boundary between Liu-Kiu and Japan The isle Who-sher Yonagumi Island Yaeyama Islands Shang-chen king and his mother The Little Liu-Kiu Tsai ching