Koyajima is one of the small rocky islets that lie in the sea around Okinoshima, in the strait between Kyushu and the Korean peninsula, and like its neighbours it is part of the World Heritage listing of the sacred island and its related sites. It is a barren place, with bare rock and sea birds, and nobody lives here. The islets near the main island were treated as part of the sacred zone, and sailors steering across the Genkai Sea used them as marks and as places to ask for protection.
The Genkai Sea is rough, cold in winter and subject to strong currents, and it has swallowed a great many ships. The Munakata fishing communities have lived beside it for over a thousand years, and the shrines along the coast at Munakata and on Oshima are dedicated to three goddesses who protect travellers on the water. The priests who lived at Okinoshima held rituals before and after each crossing, and the ancient envoys to China and Korea made offerings before leaving.
On the mainland, the coast road from Fukuoka to Kitakyushu is a pleasant ride, with sea views, pine trees and small harbours. Munakata Taisha is a major Shinto shrine, with a modern treasure hall displaying the finds from the island, including gold rings, glass beads and a Sasanian cut-glass bowl, and a visit there is the best way to see the objects without the restrictions of the island. The shrine is quiet, beautifully kept and shaded by old camphor trees. Parking for motorcycles is available, and entry to the grounds is free, with a modest fee for the treasure hall.
Fuel and food are in Munakata, which has convenience stores, fuel stations and restaurants serving grilled fish and sashimi, and there are small ports with ferries to Oshima. Check the timetables, because the sea can be rough and ferries are cancelled at short notice. The best seasons are spring and autumn, when the air is clear and the sea calm, and typhoons are a concern from August to October. In May, on the anniversary of a naval battle that took place in these waters in 1905, a ceremony is held on Okinoshima with a small number of men permitted to attend.