In this study, contrastive tones in six dialects of Japanese spoken in Yakushima are analysed as lexical tone systems in which either of the two distinctive tone contours realizes an accentual phrase according to the tonal feature of the initial word of the phrase. Given that spontaneous speech data are available for analysis, a special focus of this study is the presence of the right edge tones in both contours in five out of the six dialects, a feature shared by the Kagoshima and Tanegashima dialects. A tentative reconstruction of the three lineages is presented on the assumption that the characteristic LHL on the left edge of the type A contour in Yakushima is an innovation rather than a case of retention.