we just got back from a trip to Japan that included a few days in southern Kyushu. I recommend spending some time on the Miyazaki coast. Heading south there are the Easter island replica statutes at Sunmesse, the cliff-side Udo cave shrine and the castle ruins at Obi. The island shrine off Aoshima is also worth a stop and there are some nice beachside bars in the area as well. We also spent a day at the natural hot spring onsen in Kirishima. You can actually see jets of steam shooting out of the ground. If we had more time we would have explored Kagoshima and the sakurajima volcano.

Enjoy your trip!