Kuroshima is a small, flat coral island in the Yaeyama chain, sitting between Iriomote Island and Ishigaki Island. The island is famous for having far more cattle than people -- roughly 3,000 cows to a few hundred residents -- earning it the nickname "Cow Island."
Sea turtles come to nest on Kuroshima's beaches every summer, and the island hosts a lively turtle festival each February. The pace of life here is genuinely slow: you can cycle around the entire island in under an hour, passing through pastures, sugar cane fields, and quiet beaches with hardly another person in sight.
A high-speed ferry from Ishigaki takes about 25 minutes. There is little in the way of shops or restaurants, so bring what you need or eat at one of the few minshuku guesthouses.