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Kohama Island Shin'yō Boat Tunnels
Taketomi Town, Okinawa Prefecture

The small island of Kohama, part of the Yaeyama Islands east of Taiwan, is located between Ishigakijima and Iriomotejima. Kohama has four tunnels that were constructed near the end of World War II to hide shin'yō explosive motorboats that the Japanese Navy planned to use in suicide attacks against Allied ships if they approached the island.

The shin'yō boat tunnels can be reached by walking east along the beach from the ferry terminal a little more than a kilometer. The tourist guide map for the Kohama Island marks the location of the tunnels, but there is no sign to provide any historical information regarding them.

The entrance to the first tunnel can be seen easily from the beach. The entrances to the other three tunnels are somewhat hidden by heavy undergrowth. The tunnels  were constructed in a cliff near the beach and are about 25 meters in depth.

The first three tunnels from the beach remain in good condition about 70 years after they were constructed. In comparison to the second and third tunnels from the beach, the first tunnel has quite a bit of rubbish inside, probably due to its easy access from the beach. In contrast to the first three tunnels, the fourth tunnel is almost completely filled at the entrance with rubble, sand, and rocks, so it cannot be entered safely.

View from entrance of first shin'yō boat tunnel from beach

The 38th Shin'yō Special Attack Squadron was stationed first at Kohama, but it was later reassigned to Miyara Bay on Ishigakijima. The 38th Shin'yō Squadron only trained once at Kohama during the night, but it could not continue due to the constant threat of enemy air attacks. The 26th Shin'yō Special Attack Squadron, which arrived at Ishigakijima on March 1, 1945, was stationed at Kohama Island until the end of the war.

View from entrance of second shin'yō boat tunnel from beach

From September 16 to October 21, 1944, the 50 shin'yō boat pilots in the 26th Shin'yō Special Attack Squadron trained in Nagasaki Prefecture at the Kawatana Torpedo Boat Training School. The pilots were selected from the 13th Kō Class of the Yokaren (Preparatory Flight Training Program) from Nara Naval Air Group. In addition to the 50 shin'yō boat pilots, the 26th Shin'yō Squadron had 7 officers, 18 headquarters personnel, 35 maintenance workers, and 74 base workers for a total of 184 members.

View from entrance of third shin'yō boat tunnel from beach

The 26th Shin'yō Special Attack Squadron officially formed on December 5, 1944. The squadron had 52 one-man Model 1 shin'yō motorboats loaded with explosives for suicide attacks to crash into enemy ships. The Pacific War ended without the shin'yō squadron's boats ever making a sortie to attack.

View from entrance of fourth shin'yō boat tunnel from beach

On September 13, 1945, when returning to the mainland after the end of World War II, 26th Shin'yō Squadron Commander Lieutenant Junior Grade Yūji Hikino, one shin'yō boat pilot, and one maintenance worker lost their lives due to heavy wind and rain. Five 26th Shin'yō Squadron members in total lost their lives during the war.

View of sea from beach next to first shin'yō boat tunnel

The section on the 26th Shin'yō Squadron in the two-volume history of the Shin'yō Special Attack Corps published in 1990 by the Shin'yō Association has a photograph of a monument inside of one of the tunnels to remember squadron members who died in the war [1]. However, during a visit to Kohama Island in November 2013, there were no traces of the monument that could be found.

The historical information about the 26th Shin'yō Special Attack Squadron is from pages 56-7 of the following book:

Shin'yō Association (Shin'yōkai), ed. 1990. Ningen heiki: Shin'yō tokubetsu kōgekitai (Human weapon: Shin'yō Special Attack Corps). Shirō Arai, general editor. Two volumes. Tōkyō: Kokushokankōkai.

The historical information about the 38th Shin'yō Special Attack Squadron is from pages 80-1 of the book.


1. Shin'yō Association 1990, Volume 2, 57.