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Nishiki Secret Base Museum – A Mysterious Landlocked WWII Naval Base Discovered in 2015

Learn about life in WWII-era Japan

Opened in 2015, the Nishiki Secret Base Museum lies atop a former naval runway in the town of Nishiki in the Hitoyoshi-Kuma Region of southern Kumamoto Prefecture.

The museum consists of an aboveground exhibition area along with a network of tunnels dug into the earth below the main museum buildings.

I had the opportunity to take a short visit in August 2022 and found the museum very interesting and informative. It is definitely worth the trip if you’re in the area or are a WWII history buff.

Basic Info

Nishiki Secret Base Museum isn’t located very close to an operating train station, so you’ll need a car to get there. The museum itself is just 10 minutes from the Hitoyoshi exit on the Kyushu Expressway and is pretty easy to find.

Basic admission costs ¥800 for adults and includes access to the exhibits and a basic tour of the underground tunnels (the torpedo assembly rooms). An additional ¥500 gets you the deluxe tour, which also includes a look at the underground barracks, the communications room, and the strategy room.

Multilingual Support

A lot of the basic signage is in English, but the main exhibit explanations are all in Japanese only. Tours are also available only in Japanese.

Audio guides are available in multiple languages. I unfortunately didn’t have the opportunity to try one out and therefore cannot vouch for their quality.

Construction of the Base

Construction on a naval base in the town of Nishiki began during WWII in November 1943. The landlocked location may seem like an odd spot for a navy base, but because Nishiki is located in a secluded valley nearly equidistant from naval bases along the east, west, and south coasts of Kyushu, it made it a logistically advantageous spot to train pilots who would later serve along the coasts and at sea.

The base consisted of a 1,500-meter long runway, headquarters, training hall, and barracks and opened for training operations in 1944.

How the Base Was Used

The base was subsequently bombed by the US twice and, with the tide of war rapidly turning against Japan, the base was then used as a training base for kamikaze pilots. As Japan began to prepare for a full-on homeland invasion, the base was again converted into a defensive position and a large network of underground tunnels was constructed to fortify the area.

As the war ended without an invasion, the base was never used as a point of defense and was abandoned after only 1 year and 9 months in operation. Interestingly, although the locals were aware of the aboveground facilities and runway, the underground tunnels were kept secret. When locals discovered the tunnels after the end of the war, they assumed they were air raid tunnels and used them to store farming equipment.

It was only in 2015 that these tunnels were found to have actually been part of a complete and functioning underground navy base. It was then when this museum was founded and research began on exploring the purpose and activites of the base. Because the base was a secret, there is very little surviving documentation and many details of the base remain a mystery.

The Museum

The aboveground section of the museum is compact and consists of a reception area, small souvenir shop, restaurant, training plane display room, and exhibition area.

Just past the entrance, you’ll find a life-sized replica of a Yokosuka K5Y biplane, known as akatonbo (赤とんぼ “red dragonfly”) due to the easily-recognizable paint scheme used for all Japanese military training aircraft.

The exhibition room is separated into two sections: a library and video interview area, and a chronological exhibition area. The library houses books in Japanese related to WWII and a few booths with videos of interviews with WWII survivors and locals. Photography is prohibited in the exhibition room, so unfortunately I don’t have any pictures for this section.

Main Exhibition Area

The exhibition area offers a chronological look at the origins of the base, daily life for the soldiers and locals living nearby, and how the base changed over time. Locals donated/loaned many of the relics on display. Many exhibition photos show the soldiers at work on the base, many of whom look so young that they could be in elementary school.

One major point of the museum is the production of turpentine. During WWII, the US stopped supplying Japan with oil in retaliation for its expansion in China. The need for oil acted as a motive for Japan to attack the US, and the lack of oil stunted Japan’s ability to fuel its war machine. Turpentine, made by processing the roots of pine trees, was an adequate fuel substitute, and the locals of Nishiki and soldiers at the base occupied much of their time with its manufacture.

Another major point of the museum was that the base acted as a training center for tokkotai pilots, known to Westerners as kamikaze pilots. Pilots trained in Nishiki before being assigned to suicide missions in the Pacific. The museum features a number of relics related to the kamikaze pilots, including a senninbari, diaries, and a good luck flag.

One of the last exhibits of the museum explains the story of Mr. Fumoto, a Japanese soldier who participated in the capture of the USS Wake. Fumoto held onto the ship’s US flag and kept it with him throughout the war because he believed that, even though the flag he carried was the flag of the enemy, it was the flag of a nation and should treated with respect. After the war, he returned the flag to the United States. The final exhibit tells his story, with pictures of Mr. Fumoto with the flag and a letter from the US consul to Japan offering his gratitude for its safe return.

The Underground Tunnels

The underground part of the museum is only accessible during one of the regularly scheduled tours (each tour is about 30 minutes long and the tours are held hourly). Your admission includes The guided tour is included with your admission.

A shuttle van offering free rides to and from the caves is available for people unable to walk down the 200 or so stairs from the museum to the cave entrance.

The tour starts with a quick explanation of where the original runway was located with respect to the museum. The tour then heads into thick grouping of trees next to the museum and down a long series of stairs.

At the bottom of the stairs is a shrine. The shrine has a small courtyard where the senior officials of the base supposedly gathered in the final days of the war to hear the news that Japan had surrendered.

Behind the shrine is a short cliff face with a number of large holes just a couple dozen meters past the shrine grounds.

These hand-carved tunnels were dug to be large enough to carry large machinery in and out of the caves. The basic tour visits the torpedo assembly rooms just inside the large cave entrance above.

Torpedo Assembly Rooms

In contrast to the rough, bare stone of the main tunnels, the walls and ceilings of the two torpedo assembly rooms are reinforced with concrete to prevent cave-ins in the event of a torpedo mistakenly exploding. The two torpedo rooms lie next to each other but the entrances are offset slightly so that again, if a torpedo goes off, it affects only one isolated torpedo room rather than both rooms together.

One of the torpedo rooms has a full-size replica of a WWII-era Japanese torpedo so visitors can get a sense of the size of the ordinance that was worked on in these cramped quarters.

Although underground, the air in the tunnels is quite warm and extremely humid. Life in these tunnels together with hundreds of other people must have been extremely unpleasant .

Conclusion & More Info

In conclusion, the Nishiki Secret Base Museum is a great place to stop by if you are in the Hitoyoshi-Kuma area. Even though WWII happened less than a century ago and affected life in Japan so deeply, there are surprisingly few museums and historical sites showing what life was like in wartime Japan. The Secret Base Museum offers an important look at the hardships of war and gives visitors a good idea of what life was like in WWII-era Japan.

If you’re looking for more to do in the area, be sure to check out Hassenba in Hitoyoshi City for good food, a nice view of the Kuma River, and boat rides. The secluded village of Itsuki is located about 35 minutes north of Nishiki and is a great place to relax and enjoy a bungee jump or two.


Nishiki Secret Base Museum
錦ひみつ基地ミュージアム

Address: 2-107 Nishi, Kinoue, Nishiki-machi, Kuma-gun, Kumamoto-ken
Hours: 9AM-4PM (open until 5PM in July and August, hours subject to change)
Price: Admission ¥800 (adults), Extra tour ¥500 (adult)

Originally from NJ, USA, Jason has lived in Kumamoto since 2006. He currently co-runs Adastra Co., Ltd. and heads Shirakawa Banks (Shirakawa Night Market, etc.). He enjoys pretending he is playing Gran Turismo as he drives very very slowly up the mountains of Aso in his kei-van.

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