Hirajima belongs to the same far-flung Ogasawara chain as its neighbours, a scatter of small islands and reefs in the Pacific about a thousand kilometres south of Tokyo. Its name simply means flat island, which suits something low and unassuming compared with the sharp, forested peaks of the bigger islands nearby. There are no roads on it in any real sense, and there is no way to ride to it, so this is a sea-level look at a protected place.
The story of the chain is a tangle of nations. Polynesian and Micronesian travellers may have passed this way long ago, and Spanish and Dutch sailors marked the islands on their charts. The first permanent settlers in the 1830s were a mixed group from the Pacific and the West, led by a man called Nathaniel Savory, and their descendants lived here when Commodore Perry's ships called in 1853. Japan claimed the islands in the 1870s, and after the Second World War the United States ran them until they were handed back in 1968. That history still shows in the family names and the English words in the local dialect.
Offshore, the water is clear and the colours range from deep navy to a startling pale turquoise over the reefs. Divers and snorkellers will find coral gardens and sharks, and the chance of seeing dolphins on the boat trip is high. Birds nest on cliffs and ledges, and some species breed nowhere else.
To get anywhere near it you need to take the ferry from Tokyo to the main island of Chichijima, a journey of roughly twenty-four hours, then arrange a boat. Chichijima has a small port town with fuel for the scooters and cars that serve the islanders, along with simple restaurants and guesthouses. Book ahead, because rooms are limited, and expect sea conditions to decide your schedule.