Okuoikojo Station as seen from the observation deck in September 2025.
Okuoikojo Station sits seemingly afloat on a mountain lake, tucked away in Kawanehon Town, Shizuoka Prefecture. One of the most remote stops on the Oigawa Railway, celebrated for its steam locomotive runs, the station offers a view unlike anywhere else. From the nearby observation deck, you can take in the full sweep of the lake, with the little station below and mountains rising all around. The deck is fairly easy to reach by bus.
Getting to the Observation Deck
The journey starts at Senzu Station, the transfer point between the Oigawa Railway main line and the Ikawa Line, where Okuoikojo Station is located. As of September 2025, however, typhoon damage from 2022 has left the section between Kawaneonsen-Sasamado and Senzu closed to rail traffic, so we made our way there by car.
From Senzu Station, board the Kanzo Line bus — but plan ahead, as it runs just once a day in each direction, departing Senzu at 11:00 AM. After a 23-minute ride, get off at the Kojo-iriguchi stop, then follow a short two-minute walk to the observation point overlooking Okuoikojo Station.
The view from above is worth every bit of the effort. Below, Sesso Lake, the dam lake cradling the station — is spanned by a vivid red structure locals call the Rainbow Bridge. The station itself perches at the end of a slender peninsula reaching out into the water. In the crisp mountain air, the landscape shifts with the seasons and the light, offering something a little different each time you look.
The Descent to the Station
From the observation deck, a path leads down to the station, but don't let the downhill direction fool you. The route involves steep slopes and flights of stairs, and it's a genuine workout. Going back up would be harder still, which is why the bus-then-train direction is recommended. A notice at the Senzu Station bus stop puts it plainly: if you're carrying large luggage or traveling with young children, this path is not particularly recommended.
It's technically possible to visit the station by train first and then catch the bus back up to Senzu, but the descent is far more manageable than the climb. There is also a dedicated parking lot for the station, though drivers should know that reaching it involves the same steep road on foot.
The walk down takes around 20 minutes, passing over a bridge that runs alongside the railway tracks. Arriving at the station, the surroundings feel surprisingly welcoming. There's a "Bell of Happiness" to ring, and a small café that opens on selected days.
Looking out across the lake, you'll notice an old railway bridge standing in the water. This is a remnant of the original line, used before Okuoikojo Station came into existence. When the Nagashima Dam was built across the Oi River, part of the Ikawa Line disappeared beneath the rising water. As a result, a new stretch of track was built in its place when the station opened in 1990.
Japan's Only Abt Rack Railway
The new alignment came with a consequence: steep gradients that conventional trains couldn't handle. The solution was the Abt rack railway system, still in use today between Abt Ichishiro Station and Nagashima Dam Station. A toothed rack rail runs between the tracks, and gears on the locomotive mesh with it to maintain control on the severe inclines — climbing and descending what would otherwise be an impossible slope.
During our trip, the 12:18 PM train toward Senzu pulled in on schedule. Boarding it meant experiencing the only stretch of rack railway left in Japan.
Leaving Okuoikojo Station, the train calls at Nagashima Dam Station before tackling the descent to Abt Ichishiro Station — a gradient of 90 per mille, meaning the track drops 90 meters (around 295 ft) for every 1,000 meters traveled. It's the steepest railway gradient in the country, and riding it, you can feel exactly why ordinary trains would never manage it.
The Locomotive Change
At Nagashima Dam Station, passengers are invited to step onto the platform and watch as a special electric locomotive is coupled to the front of the train. The Abt section requires a different kind of power, as this stretch of track is electrified, and the contrast with the small diesel that had been doing the work until now is immediately striking. The electric locomotive is a considerably more muscular machine, built for the demands ahead.
Once the coupling is complete, the train eases away from the station. To the left, the great wall of Nagashima Dam fills the view, and from somewhere beneath the floor comes a new sound: the low creak and grind of gears biting into the rack rail as the locomotive takes hold of the slope.
At Abt Ichishiro Station, the electric locomotive is uncoupled and the rack rail ends. Stepping down to take a closer look at the toothed rail set between the tracks, you get a real sense of the engineering muscle required to hold a train on a gradient like that. From here, the line returns to normal operation, and the train rolls into Senzu at 1:19 PM.
The whole outing takes just two and a half hours, yet packs in a breathtaking station perched over a mountain lake and a ride on a piece of living railway history.
Trains Left Waiting
Back at Senzu Station, a quieter sight catches the eye: a row of former Nankai Railway cars sitting idle on a severed stretch of track, their paint peeling, stranded by the line closure with nowhere left to go.
Should the main line eventually reopen, it's well worth continuing on to Shin-Kanaya Station, where the railway depot is home to the steam locomotives and the other remarkable rolling stock that have made the Oigawa Railway famous.
Note: This article was written in September 2025.
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(Read the article in Japanese.)
Author: The Sankei Shimbun
