Cultural Properties of the Munakata Region
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Oshima in the Age of Isolation |
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During Japan’s period of isolation in the Edo period (1603–1867), Oshima functioned as a guardian island for both Okinoshima and the Genkai Sea. The shogunate viewed Christianity as a threat to its rule and had banned the religion in 1614. This escalated to the expulsion of the Portuguese from Japan in the late 1630s after an uprising by Japanese Catholics, and marked the beginning of two centuries of national isolation. Under the Kuroda domain of Fukuoka, Oshima became a coastal outpost, with guards stationed to watch for foreign vessels.
The Portuguese missionaries incident
On May 12, 1643, a foreign ship carrying four Portuguese missionaries and several other Christians arrived on Oshima. The group was captured by the island’s guards, and residents involved in the detainment were rewarded. A plaque remains at the landing site.
Following the incident, the Kuroda domain strengthened the island’s defenses, adding watch posts at Tsuwase on the west coast, Iwase on the north coast, and the summit of Mt. Mitake (224 m). Oshima became the base for officials overseeing Okinoshima, from where guards were dispatched to serve 50-day rotations on the sacred island. Those permitted to land on Okinoshima were required to conduct various purification rituals and observe a period of abstinence at Nakatsu-miya on Oshima before making the crossing. The practice of misogi (ritual purification in the sea), which continues today, was first recorded in this period.
Aoyagi Tanenobu’s record
Scholar and Kuroda retainer Aoyagi Tanenobu (1766–1836) was appointed as overseer of Okinoshima in 1794. Before sailing to his post, he spent ten days on Oshima undergoing purification rituals, including misogi and a climb to the summit of Mt. Mitake. He recorded these observances in his diary, Okitsushima Sakimori Nikki (“Diary of an Okinoshima Watchman”). He also described the island’s landscape, local taboos, and his sense of reverence upon reaching Okinoshima. His accounts provide a valuable record of how Oshima functioned both as a spiritual gateway to Okinoshima and as part of the domain’s maritime surveillance system. |
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