Yoshimi Caves & WWII Tunnels
as I found them; but could be 
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Not strictly speaking in Tokyo, but just outside in Saitama Prefecture, yet best reached from Tokyo, this is a dual site, one ancient, the other WWII-related. The former is the “100 Caves of Yoshimi”, a cluster of burial chambers from the Kofun period (300 to 538 A.D.), the latter a network of tunnels driven into the mountain below to house underground arms production towards the end of WWII. It is obviously those tunnels that are of more interest from a dark-tourism perspective.
More background info: The ancient burial tombs carved into the sandstone cliffs by the Ichino River about a millennium and a half ago were only rediscovered by archaeologists in the late 19th century. They are allegedly the largest cluster of such burial chambers in all of Japan. Despite the name the “100 Caves of Yoshimi” they actually number over 200.
A few of those towards the bottom of the cliff side were lost when a second operation of drilling into the mountain started in 1944, this time for military purposes.
Just as in Nazi Germany, where production sites were relocated underground or into mountains (see e.g. Mittelbau-Dora, Ebensee) as Allied air raids intensified, so did Imperial Japan try to secure some of its military production sites in such a way once the Japanese mainland had become within range of American air attacks (see also the Center of the Tokyo Raids and War Damage!).
In this case it was the Nakajima Aircraft Company, whose main aircraft-building plant had become a target for repeated raids from the air, that decided to create a new production facility a) at a safe distance from central Tokyo, and b) inside a mountain, away from view and falling bombs. The underground factory was to make either munitions and /or aircraft engine parts (different sources vary as to which exactly).
It was a massive undertaking. Over eight kilometres of interconnected tunnels, each 4 metres wide and between 2 and 4 metres high were planned. To do the actual digging work, over 3000 Koreans were requisitioned (who had been doing forced labour elsewhere before, such as in coal mines – see Hashima!). Some 80% of the tunnel system was finished between September 1944, when work began, until the end of the war a year later. The production facilities never actually moved into the unfinished tunnels (unlike at the Mitsubishi tunnels in Nagasaki).
Today the site is primarily a visitor attraction because of the ancient caves/burial chambers (of course, since in mainstream tourism older always means better), but the WWII-era tunnels were also made accessible – except when I went there I found them closed (see below).
What there is to see: Not much. I had read about the WWII tunnels and seen cool photos online, so I was very much looking forward to finally seeing them with my own eyes when I made the long journey (see below) there in late April 2019.
However, when I got there, paid the admission fee to the complex and started looking for the entrance(s) to the WWII tunnels I found all of them blocked off. There were photos of them in the brochure I was given at the ticket office and so I went back and pointed at those pictures with a questioning expression on my face. The language barrier was too great to get any explanation, but all I got was a simple “sorry, closed”.
So had I come all the way out here in vain? Not quite. From three blocked-off tunnel entrances I was able to at least get a good glimpse inside and take a few photos, even if it meant I had to step over the no-admission-beyond-this-point signs to get to the bars blocking the entrances.
Whether the closure of the tunnels for visitors will be temporary or for good I cannot say. In the photos of the main entrance I had seen online it looked like you could just walk in, not even a door in sight. When I got there I found this entrance blocked and with a metal door firmly padlocked. However, inside the lights were still on. I had seen from those photos online that the inside of the tunnels once publicly accessible were well lit, only barred side tunnels were left dark. So I had to wonder, if access to those main tunnels is now also disallowed, then why leave the lights on? Maybe I was just unlucky and some refurbishment work was ongoing? Or maybe it was because of the holidays? (But then again, why was the rest of the site open then?)
Whatever it may be, I was obviously a bit disappointed.
I still had a quick look at the old burial chambers, but, to be frank, I failed to muster much enthusiasm for them. I crawled into one (they are low and narrow) and peeked into another where through the bars some luminescent moss was visible (another thing these chambers are apparently remarkable for). But I gave the museum with ancient artefacts and all the gift shops and food outlets a miss. Other than the inaccessible WWII tunnels the site was a bit too touristy for my liking. Mind you though, that's only touristy in the domestic sense. I didn't see any other Westerners all the time, neither at the site itself, nor on the walk there or even on the train out to Saitama Prefecture. Only as the train back was approaching Shinjuku did other Westerners get on.
On balance, had I known the WWII tunnels were closed I probably would have spared myself the time and effort it took to get there. Since I cannot say whether the tunnels may reopen at another time I'll have to leave it to your own judgement as to whether or not to take your chances …
Location: Far out, some 30 miles (50 km) north-west from central Tokyo, in Saitama Prefecture, just east of Higashimatsuyama.
Google Maps locator: [36.0396, 139.4214]
Access and costs: in a rather remote spot, but doable from Tokyo; not free, but not too expensive either.
Details: It is a long, long way from Tokyo, but doable. First you have to get a local train on the Tobu-Tojo Line to Higashi-matsuyama; the trains are quite frequent and take about 50 minutes from Ikebukuro Station in Tokyo (which itself can be reached from the centre by the Yamanote JR circle line and three metro lines).
From Higashi-matsuyama Station you can get a local bus for five stops to cut walking time, or walk it all the way, which will take something like 20 to 30 minutes. From outside the station take the main road perpendicular to it heading east. Keep walking in more or less a straight line until you come to a T-junction. Turning right takes you across a bridge over the river. Turn left there and stay on the main road until you pass a Buddhist temple, then take the small road on the left and this takes you straight to the entrance. From the bus stop just before the bridge across the river it's 8 to 10 minutes' walk.
Opening times: daily, all year, from 8:30 a.m. to 5 p.m. (that's for the whole Yoshimi 100 Caves site – it does not mean the WWII tunnels will be open at the same time).
Admission: 300 JPY
Time required: If you can get into the WWII tunnels perhaps 20 to 30 minutes or so, without access to those it really depends on how much you get out of exploring the ancient burial chambers and tourist facilities. I set off back pretty quickly. Whether it's worth the three hours or more of travelling time to get there and back is also a factor to consider.
Combinations with other dark destinations: None anywhere near, unless you count the glimpse of an abandoned cave hotel that you pass en route from the bus stop to the Yoshimi caves entrance (see photo below). But you can't go inside that either.
However, I did make my way from here to the Hitachi substation ruin afterwards (changing into the Seibu-Hijama line at Honkawagoe and then Seibu-Shinjuku Line at Kodaira to get to Tamagawajosui) and then even onwards to the Chofu hangars. It was a very long day with hours spent on trains, buses and the metro … I'm in no hurry to repeat something like this.
Combinations with non-dark destinations: The main parts of the site can be called a non-dark, more mainstream attraction, even though the notion of burial chambers may trigger associations with dark tourism too. But the way the site is commodified, in typical Japanese tourism fashion, it is quite clearly not considered dark.
Other than this, there are a couple of temples nearby, as well as some hiking trails in the woods, but nothing of particular tourist interest. Head back to Tokyo for that.
