From an excellent blog:
So, I'm wondering, this guy, Shun, wrote a book available here, but there seem to be no English translations. Has anyone heard of this book before? Does anyone know if it's available in English anywhere?
This is an old story, but I still like telling it. Japanese researcher Shun Akiba has apparently discovered "hundreds of kilometers of Tokyo tunnels whose purpose is unknown and whose very existence is denied."
But a search around the Japanese web gives the book a pretty low rating and a pretty poor opinion of the guy. Most reviewers point out that no one has "found secret tunnels" - the book is a collection of "urban legends" about tunnels, and combined with known tunnels, to make a huge conspiracy theory... The thing is, the tunnels that have been "found" are all normal tunnels (access tunnels for the subway, shipping tunnels, utility tunnels, etc) and there is no room for a web of secret tunnels. The Tokyo underground is packed as it is - there honestly isn't much room to squeeze anything secret in there.
Apparently 90% of the book is the author offering increasingly more outrageous theories for these tunnels, with no actual research or exploration. A couple reviews point out that he didn't even do the most basic of research - I guess the only "secret" tunnel he did enter can be looked up and is listed as an unfinished bomb shelter that began construction during the war but was abandoned at the end. (Not all that strange.)
I myself had a laugh at a quote from the guy saying that there were secret tunnels in a specific spot (including map, apparently), with a reviewer linking to a map showing a grid of very non-secret utility tunnels in the exact same spot. The author's response was that the *secrecy* of the tunnels is being denied, not that they are there. He seemed oblivious to multiple reviewers pointing out that as they are mapped, known, and being used for utilities... It was kind of hard to call them "secret".
I wouldn't have very high hopes about this.