| Ōzushima | |
| Image Map Alt: | Map showing the position of Ōzushima in the Inland Sea of Japan |
| Native Name: | 大津島 |
| Native Name Link: | Japanese language |
| Location: | Seto Inland Sea, Japan |
| Coordinates: | 34.005°N 131.7075°W |
| Archipelago: | Japanese Archipelago |
| Area Km2: | 4.77 |
| Elevation M: | 186 |
| Country: | Japan |
| Country Admin Divisions Title: | Prefecture |
| Country Admin Divisions: | Yamaguchi Prefecture |
| Country Admin Divisions Title 1: | City |
| Country Admin Divisions 1: | Shūnan |
| Population: | 227 |
| Population As Of: | 26 May 2020 |
, or Ozu Island, is an inhabited island in the Inland Sea, Japan. Administratively, it forms part of the city of Shūnan, Yamaguchi Prefecture. Ōzushima is also known as "Kaiten Island".[1] [2]
Situated in the Seto Inland Sea across the exit from Tokuyama Bay and formerly two islands, Ōzushima and are said to have become one some four hundred years ago.[3] [4] Gently curved, long, and thin, and with a outline that somewhat resembles a misshapen Y, today's Ōzushima extends some from north to south, and has an area of .[3] There are a number of small settlements along the coast, including and, the centres for the island's masons and stoneworkers, the farming communities of and, and the fishing hamlets of and .[4] Parks on the island include Ōzushima Park and Mashima Park, while part of the island and its surrounding waters is protected within Setonaikai National Park.[4] [5] The southern coastline is suffering from severe coastal erosion.
On Mashima, the southern end of the island, may be found a five-petalled variety of narcissus known as . Bulrushes (as featured in the myth of the Hare of Inaba) grow a short distance from Setohama port in paddies that were brought into cultivation during the Edo period but now lie abandoned, while at Amagaura there is a or celebrated old-growth tree, a Camellia japonica some three hundred years old, in height, and in circumference.
The name of the recently formed city of Shūnan, in which Ōzushima is located, is a portmanteau of two characters (周南) that denote its situation in the south of old Suō Province.[6] In early-modern times, Ōzushima formed part of (once territory owned by Tōdai-ji), a flourishing market town along the San'yōdō in Tokuyama Domain, the daimyō of which came from a branch of the Mōri clan, lords of Chōshū (or Hagi) Domain.[4] [7]
Like nearby, Ōzushima is a good source of high-grade granite, which was quarried for Ōsaka Castle: one block (whether cut for its original construction by Toyotomi Hideyoshi, as part of Mōri Terumoto's contribution,[8] or for its rebuilding, by Tokugawa Hidetada after the Siege of Osaka, still lies on the island, in length, both in width and height, and weighing some .[9]
In 1748, a ship from, an island in Hakata Bay, involved in the Kuroda Domain rice trade, and laden with rice, foundered off the island; ten bodies washed ashore and were buried on Ōzushima; five of their gravestones are inscribed, attesting to contact between the two sets of islanders—some of the stones were sent from Nokonoshima; the ten are honoured in an annual memorial service on the occasion of Tanabata.[9] [8]
During the Great Pacific War, the island served as a testing and training base for the Imperial Japanese Navy's Special Attack submarine force, the Kaiten (manned torpedoes).[1] With its origins as a testing range from 1938 for the Type 93 "oxygen torpedo", for construction of the Kaiten base, eight large caissons were towed over from Ōita Prefecture, the first in October 1943, the last in October 1944, with five further small caissons produced on Ōzushima.[10] Opening in September 1944, this base was the first of what would be four such facilities (the others following in nearby Hikari, in November, and Hirao, in March, opening in what is now Hiji, Ōita Prefecture, in May 1945).[11] Remains of the base on Ōzushima include a tunnel in length and in height, cut through the rock and used to transfer Kaiten by a rail tack to and from the maintenance area, maintenance facilities that extend from the port area of Mashima to the now closed Ōzushima Elementary School, an electricity transformer station, concrete bridges, staircases, an observation station on a rise overlooking the torpedo testing area, a firing test evaluation office, a storage facility for hazardous materials, kitchens, and barracks; there was also a seaplane hangar, while walls were built to keep out the islanders and maintain secrecy as to the operations within.[10] [9] As confirmed by base members and attested by archive materials, the Yamato could be seen clearly from the torpedo observation station at her final anchorage some off the southeast coast before departure on her final mission.[10] Also on the island, and surviving in part, developed between November 1941 and May 1943 to protect Tokuyama Port and other nearby military facilities, on the summit of Mount Ōzu, the island's highest point, was an anti-aircraft battery, which in 1943 had five guns and a detail of fifty-four men.[10]
In recognition of its historic significance, the Ōzushima Former Kaiten Firing and Training Base was in 2006 listed as a by the Japan Society of Civil Engineers.[10] [12] Also, it is due to this element of Ōzushima's past, commemorated at the Kaiten Memorial Museum, surrounded by cherries that flower and fall in the spring, that the island is sometimes referred to as "Kaiten Island".[9] [2]
Post-war and in recent decades, the demographic changes affecting the country have seen Ōzushima's population decline from a few thousand to a couple of hundred (269 in 2009,[4] 227 in 2020[9]), with many of those remaining of retirement age.[1]
See also: List of Important Intangible Folk Cultural Properties.
Cultivation of tobacco and mikan was once widespread.[3] Output now includes marine products, such as hijiki and wakame seaweed, sweet potatoes, and sake (marketed under the label).[9] There is also generally low-impact tourism: in 2006, following the release of Yokoyama Hideo's (filmed in part on Ōzushima and centred around the story of, who died when his submarine training vehicle accidentally sank, before washing ashore after the Surrender) nearly twenty-five thousand visited the island's Kaiten Memorial Museum, an increase of over sixty percent on the three years before.[1]
Tokusanhin (a form of meibutsu) include, a dish involving broiled carrot, gobō (burdock), and tōfu, seasoned with shōyu (Japanese soy sauce), that is said to have originated on Tsushima (Nagasaki Prefecture); and, which, despite the name, are made using the island's heritage sweet potatoes.[9]
There is a ferry link to on Honshū; this is serviced by the JR West-operated Tokuyama Station, on the San'yō Shinkansen and San'yō Main Lines. As of May 2020, there were two vessels and seven crossings a day.[9]