From Okitsugū Yōhai-jo, if the weather is fine, the island of Okinoshima can be seen. Okinoshima is about 47km away and Okitsugū which enshrines Tagorihime-no-kami, one of the three Munakata goddesses, is on this island. Also the entire island is the property of Munakata Taisha and it is regarded as a sacred island. In the 4th century, located in the key point between Japan and the continent, ritual ceremonies were held on Okinoshima to pray for a safe navigation and successful trade. The remains of a ancient ceremonial place is left on the island.
Okinoshima is strictly off limits. Until 2017, a limited number of worshippers were able to land on the day of the Genchi-taisai, but today only who has special permission, such as researchers, or Shinto priests of Munakata Taisha can land on this island. Ones who land on this island must purify themselves in the sea before landing. The island is off limits to women.
From Okinoshima many ancient artifacts, such as stone implements and earthenware has been found. Many are listed as National Treasures, and are stored in the "Shimpō-kan" in Hetsugū but academic investigation has only been conducted on a part of the island and most parts are still untouched.
Okinoshima is one of the sites of “Sacred Island of Okinoshima and Associated Sites in the Munakata Region” inscribed on the UNESCO World Heritage List and the entire island is a nationally designated natural monument.