Kaijin Shrine (海神神社) also read as Watatsumi Shrine is a significant Shinto shrine located in Tsushima Island, Nagasaki Prefecture, Japan, that holds a Beppyo status. This status denotes that the shrine is remarkable and holds a significant historical importance. Kaijin Shrine is also ranked as an Ichinomiya, which means it is the highest-ranked shrine in its province. It is located near Mount Izu.

In Tsushima folklore it is said that Toyotama-hime and Hikohohodemi no Mikoto married at this shrine, and it is thus the sea god's palace.

Empress Jingu visited the area to worship at Mount Izu.

The shrine has a prominent set of Torii that are often compared to Itsukushima Shrine in how they enter water. Recent archaeological findings suggest it is one of the oldest shrines in Japan, and Itsukushima Shrine was based on it.

The shrine is associated with Kamikaze, the typhoon that stopped the Mongol invasion of Japan.

It has a Bronze Buddha statue from Korea in it. The statue is designated as important cultural property.

In 2012 a robber stole a Silla era Buddha statue from the shrine, on the same day they stole another statue from Kannon-ji but in 2015 it was returned.

Kaijin Shrine should not be confused with Watatsumi Shrine, which has a very similar Japanese name (海神社) to Kaijin Shrine (海神神社) and is located in Kobe

Kaijin Shrine is a significant shrine on Tsushima Island. It is known as the "Shrine of the Sea Kami." This shrine was the most important one in the past. It was called the ichinomiya. The shrine was originally linked to the sea deity Watatsumi. Later, it became associated with Hachiman. This association is mentioned in late Heian period sources.

The shrine's founding story involves Empress Jingū. She placed eight banners at the shrine after returning from Korea. These banners are why the shrine is connected to Hachiman. Hachiman means "Eight Banners." This led to another name for the shrine, "Hachiman Hongū." This name means "original shrine of Hachiman." This story is a local tradition. It is not confirmed by other Hachiman chronicles. Richard Ponsonby-Fane argues that Hachiman may have entered Japan through this shrine, as a Buddhist deity from Korea, and that this predated the association with Emperor Ōjin.

It is postulated that Hachiman may have been more linked to Empress Jingū in the early days of the Hachiman faith rather than her son Emperor Ojin.

This has parallels with Shikaumi Shrine which is a Hachiman shrine that strongly worships Empress Jingū and whose myths primarily revolve around Jingu's activities while pregnant with Ojin and invading the Three Han.

On Iki Island, Hachiman shrines are omnipresent. The Seven Shrines of Iki pilgrimage route is led by the Shōmo-gū. This shrine is dedicated to Empress Jingū. Three other shrines on the route are also dedicated to Hachiman.

On Hirado Island, Shijiki Shrine is the oldest and most prestigious. It is dedicated to the mythical figure Tokiwake. He was a general in Empress Jingū's military campaign.

Empress Jingū is more central to Hachiman worship on these islands than her son Ōjin. This is clear from various legends. One such story is in the Zenrin kokuhōki. It tells of Zen master Enni Ben'en encountering a storm. A woman appeared on his ship, claiming to be Hachiman Daibosatsu. She protected the ship.

Another legend is from the Ōei Invasion of 1419. It involves a fabricated story of a sea battle victory. The story mentions a powerful female leader. This figure resembles Empress Jingū. In the story, she drowns enemies herself. This mirrors another scene from Jingū's legend.

In these legends, Empress Jingū is depicted differently from traditional Hachiman iconography. Traditional images focus on male figures. These include Emperor Ōjin and the Great Boddhisattva Hachiman. The focus on Jingū suggests a unique interpretation of Hachiman worship in these areas. This might be influenced by beliefs during the wakō period.

There is also a "new" Hachiman shrine in the southern part of Tsushima. Medieval sources considered Kaijin Shrine as the origin of Iwashimizu Hachiman-gū in Kyoto.

It and many other Hachiman shrines of the region switched their deities of worship during the Meiji Restoration.

A bronze statue of the Tathagata Buddha has been returned to Tsushima, Japan. It is one of two Buddhist statues stolen three years ago. These statues are important cultural properties of Japan.

In October 2012, thieves from South Korea stole the statues. The theft happened in Tsushima. The stolen items included an 8th-century bronze Buddha and a 14th-century Avalokiteshvara. Four people involved in the theft were arrested in South Korea. They tried to sell the statues. They were sentenced to prison in 2013.

Japan asked for the statues back many times. South Korea kept them at the National Research Institute of Cultural Heritage. There were claims that Japan might have stolen them from Korea. Later, South Korea found no evidence that the Buddha statue was illegally taken to Japan. They decided to return it to Japan.

The Tathagata Buddha statue was returned to the Kaijin Shrine. It was reported to be slightly chipped. The time of the damage is unknown.

Buseoksa Temple in South Korea claimed the Avalokiteshvara statue. They said it was stolen from them by Japanese pirates. They filed a legal case to stop its return to Japan.

They argued that evidence said the statue was made at the temple in the 1330s. They argued Japanese pirates might have looted it in the late Goryeo period. The stayed in South Korea until the dispute was resolved.

The Daejeon District Court first supported Buseoksa Temple in 2017. They cited historical evidence of Japan taking the statue. But the Daejeon High Court later disagreed. They said Kannonji Temple in Japan legally owned the statue. The temple said they got the statue in a trade in 1527.

The Supreme Court's decision supported the High Court. It said there is no proof linking the old Goryeo temple to today's Buseoksa in Seosan. The decision was based on Japanese law. This law says ownership can be gained if someone has an item for over 20 years. Kannonji Temple had been a legal entity since January 1953. So the statue was returned.

The Kaijin Shrine on Tsushima Island holds a festival called Kaijin Matsuri. It takes place every September. The festival starts with music and dance. Participants wear black and white. They form a procession. Men with lances and shields lead it. They carry three portable shrines from the temple to the beach. A priest performs the kaijin ritual there. The ritual includes casting shellfish into the sea. This is to wish for a good catch for fishermen. It also supports the island's farmers.

• The festival of Kaijin Shrine in Tsushima, Japan

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