Kaijin Shrine — 海神神社

Kaijin Shrine sits on a forested hill above Asō Bay on Tsushima Island, the closest point in Japan to the Korean Peninsula. For over 1,300 years, mariners crossing the Korea Strait have prayed here to Watatsumi, the god who governs all ocean depths and currents. The shrine’s principal treasure is a wooden sword donated by Empress Jingū in the third century—a blade never meant for battle, but for calming waves. This is where mythology touches geography: Tsushima floats in the sea between two nations, and Kaijin has always stood at the threshold where divine protection meets geopolitical necessity.

Kaijin Shrine was established in 702 CE during the reign of Emperor Monmu, though its ritual lineage reaches back centuries earlier to the legendary campaigns of Empress Jingū. According to shrine records, the empress stopped at this bay on her return from the Korean Peninsula and enshrined Watatsumi as guardian of safe passage. The formal establishment in 702 coincided with intensified diplomatic missions between Japan and the mainland kingdoms. Throughout the Nara and Heian periods, official envoys to Tang China and Silla Korea performed purification rites here before departure. The shrine was designated as the Ichinomiya (first-ranked shrine) of Tsushima Province, indicating its supremacy in the island’s religious hierarchy. During the medieval period, it received patronage from both the Sō clan—feudal lords of Tsushima—and fishing communities dependent on the volatile strait waters.

Watatsumi no Kami (綿津見神) is the primordial ocean deity who appears in both the Kojiki and Nihon Shoki. He rules the three layers of the sea: surface, middle depths, and ocean floor. In the most famous myth, he welcomed the god Hoori (grandson of Amaterasu) into his undersea palace and gave him two tide-jewels—one to raise waves, one to lower them—which became instruments of sovereign power. Watatsumi’s daughters married into the imperial line; Toyotama-hime became the grandmother of Japan’s first emperor. At Kaijin, Watatsumi is worshipped specifically as protector of sailors and fishermen. His divine messengers are sea turtles, which were believed to carry prayers between the human and underwater realms.

The shrine’s founding legend centers on The Wooden Sword of Empress Jingū. When the empress returned from her conquest of the Three Kingdoms of Korea in the third century, her fleet encountered a supernatural storm in the Korea Strait. Waves rose like mountains and threatened to capsize every vessel. The empress drew a ceremonial wooden sword—carved from sacred camphor—and plunged it into the sea while invoking Watatsumi. The waters immediately calmed. Upon reaching Tsushima’s Asō Bay, she enshrined the sword on the hill overlooking the anchorage and designated it as a permanent sanctuary for Watatsumi’s worship. This sword, called the Shinken, remains in the shrine’s possession and is shown to the public only once every sixty years. Local fishermen still claim that on stormy nights, a faint glow emanates from the direction of the shrine—the light of Watatsumi watching over his domain.

The main worship hall (honden) is built in the Ōtori-zukuri style, a variation of the ancient Shinmei-zukuri architecture with extended gable bargeboard that resembles a bird in flight—appropriate for a shrine overlooking water. The structure dates to a 1677 reconstruction commissioned by the Sō clan and is designated an Important Cultural Property. The approach climbs through a forest of Japanese chinquapin and camphor trees, the same species from which Empress Jingū’s sword was carved. At the base stands a stone torii gate erected in 1591, its pillars worn smooth by centuries of salt wind. The shrine complex includes five subsidiary shrines dedicated to Watatsumi’s daughters and ocean messengers. A natural spring near the main hall, called Shionoido (Tide Well), is believed to rise and fall with the actual ocean tides fifty meters below—a hydraulic mystery that reinforces the shrine’s connection to Watatsumi’s realm.

• Reisai (August 1-2) — The annual grand festival featuring a mikoshi procession to the shore of Asō Bay. Priests perform shinji rituals on boats while offerings of sake and rice are released into the sea for Watatsumi.
• Anfune Matsuri (First Saturday of December) — A boat purification ceremony in which local fishermen bring their vessels to be blessed before the winter fishing season. Each boat receives a sacred rope and ofuda talisman.
• Monthly Tide Rituals — On the first and fifteenth of each month, dawn prayers coincide with high tide, believed to be when Watatsumi’s presence is strongest.

Early autumn—September through early November—offers clear skies and calm seas, allowing unobstructed views across the Korea Strait toward the Busan coast on the Korean Peninsula, visible on clear days. The August Reisai festival is the most atmospheric time, when the shrine becomes the center of island-wide maritime gratitude. Avoid typhoon season (July-August), when ferry service to Tsushima can be disrupted. Dawn visits reveal morning mist rising from Asō Bay, a scene that evokes the shrine’s mythological origins.