 Complete the following phrase:  Amami has a complex relationship with its southern neighbor, Okinawa. Ethnolinguistically, the languages of Amami are closer to the languages of Okinawa than to the languages of Kyushu. Politically, however, Amami shares a much longer history with mainland Japan than with Okinawa. Fragmentary sources such as a Kamakura-period map of Japan and a set of documents created by Chikama Tokiie in 1306 suggest that Amami was within the sphere of influence of the Kamakura shogunate before the Okinawa-based Ryukyu Kingdom invaded Amami in the 15th and 16th centuries. 