This island is famous for cattle and there are about 3000 cows in this island in spite of the fact that there are only 200 people. This island is completely away from modern life. for example, there are no convenience stores, no DVD rental stores, no signal on the street, etc. This island has nothing except for a beautiful beach, arguably more beautiful than those on Okinawa Island. Plus, as there are few people on the beach, and it will be rather private.
Nishi no Hama (西の浜), just west of the port, isn't much in the way of a beach, but it's a spawning ground for sea turtles during summer nights. The turtles are a protected species, of course, so viewing them is possible only under strictly regulated conditions.
The small Kuroshima Research Station (黒島研究所)  studies mostly sea turtles, and plenty of juvenile specimens can be viewed in tanks. There's also a fearsome coconut crab in a cage, as well as coral and shells on display. Entry is ¥300. Nighttime excursions to view the sea turtles are available for ¥1500.