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Oomuroyama, West Tanzawa | Moss, Clear Streams and Mt. Fuji on a Quiet 16 km Loop

2025.04.25

Quiet, and then suddenly a view. This time we went to Oomuroyama (1,587 m), which stands on the border between Kanagawa and Yamanashi. The route is a loop from the Nishi-Tanzawa Visitor Center by way of the Inukoshiji pass, through mossy streambeds and beech forest, with a snow-white Mt. Fuji for company.

West Tanzawa suits anyone who wants their hiking on the quiet side. There were nervous stream crossings and a fight with the mud, but mostly it was a day of paying attention to the forest, with just enough adventure in it.

The route at a glance

• Mountain: Oomuroyama (1,587 m) — listed among both the 100 Famous Mountains of Kanto and the 100 Famous Mountains of Yamanashi
• Area: the Tanzawa range, on the Kanagawa–Yamanashi border
• Route: Nishi-Tanzawa Visitor Center → Inukoshiji → Oomuroyama → Mae-Omuro → Kanyudosan → Shiraishi-toge → Yokisawa-deai (loop)
• Distance and time: about 16 km, around 1,400 m of cumulative ascent, roughly 8 hours of walking time (about 9 hours on the day, with breaks and filming)
• Temperature that day: 8°C in the morning. Mornings and evenings are cold even in spring, so bring something warm

Stream crossings, moss and clear water

Almost as soon as you start walking there are stream crossings, which is very much West Tanzawa. The cherry blossom had already fallen in Tokyo, but here there were still pink flowers on the trees. At 8°C, we set off for Inukoshiji.

The crossings turned out to be an adventure in themselves. I stood there more than once wondering where exactly you're supposed to put your feet, trusted my Gore-Tex boots and went — and still ended up with damp socks. West Tanzawa has a lot of crossings on bridges and stepping stones, so properly waterproof boots and a careful eye for slippery rock are both worth having.

Even so: the water runs emerald and completely clear, birds call the whole way, and the moss spreads beautifully over the rocks. It's not a trail you can walk absent-mindedly, but it's a restorative one.

The steep climb up to Inukoshiji

Once you leave the streams, the climbing starts in earnest. I'd hurt my hip slipping on another mountain a while back, so I took it one careful step at a time. From the 841 m point the trail gains height fast, and by then the breeze on a sweaty back is very welcome.

Inukoshiji (1,060 m) has an emergency shelter and a toilet. It's a pass with a legend attached: Takeda Shingen is said to have crossed it on his Odawara campaign, following dogs sent ahead to find the way. Most of the ridges in West Tanzawa are wooded, and one of the things that marks this spot out is that it opens into bright grassland. The view from the shelter is good too — a good place to stop.

And there's Mt. Fuji

On the stretch from Inukoshiji toward Oomuroyama, Mt. Fuji finally appeared, completely white. I hadn't expected pure white to be quite that beautiful, and it stopped me where I stood. Walking a ridge with Fuji in view is the highlight of this mountain.

The snack that day, incidentally, was a chocolate rabbit made from a mould I'd printed. I've been rather taken with 3D printing recently and have been making my own earrings — that sort of conversation, with that sort of view.

The summit, and a muddy way down

After a struggle with some thorny plants just below the top, we reached the summit of Oomuroyama (1,587 m) just after noon. The summit itself is surrounded by trees and has no view, but having climbed the whole way with Mt. Fuji in sight, I couldn't complain. There's a Yamanashi 100 Famous Mountains marker up there, a reminder that this peak makes both lists.

It was my first hike in a month and my legs knew it, so at the top I debated going back the way we'd come rather than completing the loop. After a rest I felt better and chose the loop — on past Mae-Omuro and the Kanyudosan emergency shelter to Shiraishi-toge. That descent turned out to be the awkward part: mud and slop, and I went down more than once. I ended up laughing about whether I'd manage to stay on the mountain at all. The full day ran to about 9 hours rather than the 8 we'd planned. Sore big toe, clear head — a very good return to hiking.

In short: for anyone who wants the mountain quiet

The best thing about Oomuroyama is how few people are on it, and how quietly you can walk. Moss and clear streams, beech forest, and a ridge running from Inukoshiji over the summit to Shiraishi-toge with Mt. Fuji in view the whole way.

Set against that, it's a substantial 16 km loop, with crossings, a steep climb and a muddy descent. Waterproof boots, gear that accounts for falling over, and a plan with time to spare. If you want to get away from the noise and spend a day properly with the mountains, this is the one I'd send you to.

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