In the sixteenth century, members of the Ouchi family were kings in all but name in much of Japan. Immensely wealthy, they controlled sea lanes stretching to Korea and China, as well as the Japanese city of Yamaguchi, which functioned as an important regional port with a growing population and a host of temples and shrines. The family was unique in claiming ethnic descent from Korean kings, and-remarkably for this time-such claims were recognized...