What Lies Beneath Kokkai-gijidō-mae: The Tokyo Subway Station That Keeps Its Secrets

I’ll be in Tokyo for a few days next week, and while most people’s itineraries focus on temples, cherry blossoms, and neon-lit streets, mine includes a few less conventional stops. Beneath the surface of this massive city lies a network of mysteries — places where ghost stories, wartime history, and political secrets converge. Some are famous. Others are rarely spoken about aloud. And one of the most intriguing of them all sits just beneath the National Diet Building.

This is the story of Kokkai-gijidō-mae Station — and the rumours of secret tunnels, hidden bunkers, and ghostly encounters that have followed it for decades.

Tokyo is a city of contradictions. It’s a hyper-modern metropolis powered by efficiency and logic, yet it’s also a city steeped in tradition, reverence, and folklore. Shrines exist on the same blocks as megacorporations. Legends are whispered about subway tunnels just as they are about mountain paths. And while Tokyo is known for its order and infrastructure, what lies beneath it tells a different story.

There have long been whispers of a shadow network of tunnels, bunkers, and restricted-access chambers beneath the city — constructed in secret during the Second World War and expanded during the Cold War. Over the years, those whispers have grown louder, particularly in areas tied to the government and the military. At the centre of it all is one subway station that sits quite literally beneath power.

Kokkai-gijidō-mae Station lies directly beneath the National Diet Building, the seat of Japan’s legislature. It serves the Chiyoda Line of the Tokyo Metro and connects via long passageways to Tameike-Sannō Station, which itself is linked to the Prime Minister’s official residence. On the surface, it functions like any other well-run Tokyo subway stop. But once you start looking closer, the unusual details begin to surface.

Journalist Shun Akiba, who has investigated Tokyo’s underground for years, has claimed that official blueprints of the station show an additional, deeper level not found on public maps. This level, he argues, was intended as an emergency evacuation platform for government officials and may even connect to a private rail line leading out of the city. These claims were partially echoed in a 2002 Tokyo Metropolitan Government report that investigated unexplained subterranean structures throughout the city. The report confirmed the existence of multiple tunnels and sealed chambers beneath government buildings, some of which lacked any documented purpose. While the report stopped short of naming Kokkai-gijidō-mae directly, its implications only fuelled existing speculation.

Stories of a wider underground network persist, with rumours claiming there are direct links between the National Diet, the Ministry of Defense, and the Prime Minister’s residence — not just through surface routes, but through a concealed system of corridors and access points. Some believe these tunnels were developed as Cold War-era bunkers, meant to protect high-ranking officials during a nuclear attack. Others suggest they predate even that, going back to Japan’s militaristic buildup before World War II. What lends these stories weight is the broader pattern seen across Tokyo. Inconsistencies in construction blueprints, suspiciously sealed stairwells, and unusual access restrictions are not uncommon in politically sensitive zones of the city.

Despite its primary association with political secrecy, Kokkai-gijidō-mae Station has also attracted a degree of paranormal interest. One of the most commonly shared experiences is the sense of being followed when walking the corridor that connects it to Tameike-Sannō. It’s a long, sterile, and mostly empty underground passageway, often described as oppressively quiet. People have reported seeing movement just beyond their peripheral vision, or hearing footsteps that don’t seem to belong to anyone visible. There are stories, repeated quietly among metro workers, of security cameras glitching when aimed at specific sections of the hallway. Phones and radios are said to lose signal abruptly, and some late-night passengers have described feeling an unexplained coldness while waiting alone on the platform.

What makes this location particularly unsettling is its connection to real, traumatic history. In 1995, members of the Aum Shinrikyo cult released sarin gas in multiple locations across Tokyo’s subway system in a coordinated terrorist attack. One of the affected trains on the Marunouchi Line was taken out of service at Kokkai-gijidō-mae Station. The attack killed thirteen people, injured thousands, and left a lasting psychological scar on the city. Though there are no widespread ghost sightings tied directly to the event at this station, the trauma associated with it lingers. In a country where spiritual energy is often linked to the emotional imprint of places, it’s easy to see why this station feels different.

Some go further than tunnels. According to fringe researchers, independent journalists, and speculation shared across Japanese forums and blogs, the restricted areas beneath central Tokyo — particularly around Kokkai-gijidō-mae — may have once been used for classified government experiments or biological research during the Cold War. These rumours often describe sealed metal doors in sections of the subway no longer accessible to the public, rumoured to be reinforced and labelled with warnings — the kind used in chemical containment zones or military facilities.

While no official records support the claims, some say these areas were designed not just for evacuation, but for testing response to biochemical threats or housing experimental equipment for disaster planning. The secrecy of Japan’s post-war intelligence efforts, combined with the shadow of U.S. involvement in Cold War contingency planning, has only deepened the speculation. Certain conspiracy-minded sources allege that sealed underground corridors run beneath the National Diet, the Ministry of Defense, and even reach older wartime bunkers repurposed for modern intelligence purposes — though no maps or whistleblower accounts have ever publicly verified this.

Japanese urban legend websites sometimes cite anonymous posts claiming that strange machinery was once heard running deep below street level during the 1980s in areas now off-limits. A few stories describe men in full protective gear entering unmarked doors late at night, supposedly during chemical testing drills. Others mention long-forgotten service elevators that descend farther than blueprints allow — always ending at floors that aren’t acknowledged by the Tokyo Metro.

It’s important to stress that none of these stories have been confirmed, and most exist only in speculative corners of the internet and out-of-print zines from the 1990s. But what gives them staying power is how they reflect genuine gaps in what is publicly known — like the confirmed existence of tunnels and sealed chambers beneath government buildings that still lack explanation. Combined with Tokyo’s deep infrastructure, historical trauma, and layers of political secrecy, these myths have become a kind of folklore in themselves.

As with many legends, the mystery surrounding Kokkai-gijidō-mae is built not just on what is known, but on what is deliberately left unsaid. The hidden floor that may or may not exist. The corridors that are just out of reach. The cameras that shouldn’t malfunction — but do. Whether this is the result of paranormal forces, historical trauma, or layers of governmental secrecy, the effect is the same: Kokkai-gijidō-mae doesn’t feel like just another subway station.

Next week, I’ll be heading there myself, not in search of conspiracies but out of curiosity. I want to see what it feels like to stand in a place where so many threads of fear, history, and the unknown are said to converge. Maybe it’ll feel like nothing at all. Or maybe I’ll feel what others have described — that subtle pressure in the air, the quiet that isn’t quite silence, and the sense that something is present, just out of sight. Either way, I’ll be paying attention.