Mt. Kuroboshi

Mt. Kuroboshi (黒法師岳, 2,068 m), on the border of Tenryu (Hamamatsu) and Kawanehon in Shizuoka, is a peak of the deep southern Southern Alps (Shinnanbu) and one of the 300 Famous Japanese Mountains.
Its summit has an unusual first-order triangulation point marked with an “×” instead of the usual “+”, and it is the southernmost mountain over 2,000 m named on the national topographic maps. No regular bus reaches the trailhead; it is a quiet, remote peak of old-growth forest and rhododendron ridges, an advanced mountain for experienced hikers. The usual route climbs from the Tonakayama forest road on the Misakubo side over Mt. Azabu and Baradani-no-kashira; there is also a long route from the Sumatakyo Onsen on the Kawanehon side via Mae-Kuroboshidake.

⚠ Access note (a remote Shinnanbu peak): Mt. Kuroboshi has no bus to the trailhead, and the forest roads are prone to landslides and closures. On the Misakubo side, the Tonakayama forest road is reached by car, or by taxi from Mizukubo Station on the JR Iida Line, up to the gate, then on foot (check the forest road’s passability in advance with Hamamatsu City and local sources). The point reachable by public transport is the Sumatakyo Onsen on the Kawanehon side (by bus from Senzu Station on the Oigawa Railway), but from there to Mt. Kuroboshi is a very long traverse over Mae-Kuroboshidake, for fit, advanced hikers. There are no staffed huts on the mountain; you need gear for tent camping or self-shelter. Water sources are scarce, so carry ample water and food, a map, GPS and a headlamp.

The base is either the gate of the Tonakayama forest road on the Misakubo side (about 20 minutes by car from the Mizukubo Dam) or the Sumatakyo Onsen on the Kawanehon side. On the Misakubo side you follow a long ridge — gate → Mt. Azabu trailhead → Mt. Azabu (1,685 m) → Mae-Kuroboshiyama → Baradani-no-kashira (2,010 m) → Mt. Kuroboshi — a day trip only for the very fit, with most parties camping near Baradani-no-kashira. The Sumatakyo side is an extra-long route from the Sumatakyo Onsen over Mae-Kuroboshidake (1,943 m) and on, requiring a night or more. The season is early summer to late autumn once the snow has gone; in the snow season the deep south becomes far more difficult.

*Information last checked: unverified

Access to the trailhead

1. [Outbound] To the trailhead (Mizukubo Station / Sumatakyo Onsen)
2. [Return] Sumatakyo Onsen → Senzu Station

1. [Outbound] To the trailhead (Mizukubo Station / Sumatakyo Onsen)

Misakubo side (main route): the nearest station is Mizukubo on the JR Iida Line, but no bus runs to the Tonakayama forest road trailhead. From Mizukubo Station take a taxi, or drive via the Mizukubo Dam into the Tonakayama forest road (by car to the gate, then on foot). Sumatakyo side: from Senzu Station of the Oigawa Railway, take the Oigawa Railway “Sumatakyo Line” bus to the Sumatakyo Onsen (about 38 min, 6 services a day). The Sumatakyo Onsen is the start of the route via Mae-Kuroboshidake. The table below shows the Sumatakyo Line.

Bus timetable ①: Senzu Station → Sumatakyo Onsen (Oigawa Railway Sumatakyo Line, outbound)

By car: on the Misakubo side use the parking spaces along the Tonakayama forest road (variable with road conditions); on the Sumatakyo side use the Sumatakyo Onsen car park. Check forest-road closure information in advance.

Reference: [Oigawa Railway bus timetable]

2. [Return] Sumatakyo Onsen → Senzu Station

If you come down on the Sumatakyo side, take the Oigawa Railway “Sumatakyo Line” bus from Sumatakyo Onsen-iriguchi back to Senzu Station (about 38 min, 6 services a day). The Sumatakyo-Onsen-to-Senzu service runs from a first bus at 6:37 to a last bus at 18:02. On the Misakubo side return by your arranged taxi or car. The deep south makes for long days, so allow ample time for the last bus.

Bus timetable ②: Sumatakyo Onsen → Senzu Station (Oigawa Railway Sumatakyo Line, return)

Reference: [Oigawa Railway bus timetable]

Route and safety notes

Misakubo route (Tonakayama forest road, main route): Tonakayama forest-road gate → Mt. Azabu trailhead → Mt. Azabu (1,685 m) → Mae-Kuroboshiyama → Baradani-no-kashira (2,010 m) → Mt. Kuroboshi. A long ridge of old-growth forest and rhododendron; the round trip from the gate is about 8–9 hours for the fit. A day trip suits only strong hikers, and a two-day trip camping near Baradani-no-kashira is safer.

Sumatakyo route: Sumatakyo Onsen → Mae-Kuroboshidake (1,943 m) → on along the ridge to Mt. Kuroboshi. Very long, requiring a night or more; an advanced traverse. Many hikers turn back at Mae-Kuroboshidake.

Huts and water: there are no staffed huts on the mountain, so overnight stays mean tent camping. Water is scarce, so carry plenty of drinking water in advance. Places to shelter in bad weather are limited, so judge the weather carefully.

Forest roads and closures: the forest roads of the deep south are frequently closed by landslides and rockfall. Check the latest passability of the Tonakayama and other forest roads with Hamamatsu City or the local tourism association in advance.

Triangulation point: the first-order triangulation point at the summit is marked, unusually for Japan, with an “×” rather than the usual “+”, a feature of Mt. Kuroboshi.

Weather and gear: at 2,068 m but deep in the southern range, be ready for sudden weather changes, strong wind, cold and losing the route. Carry a map and compass (GPS), a headlamp, rain gear, warm clothing and camping gear. The season is early summer to late autumn once the snow has gone.

In an emergency: call 110 (police) or 119 (fire/rescue). The Shizuoka Prefectural Police cover this range. Mobile-phone coverage is absent over long stretches, so file a climbing plan and go in a group.

Photo by Koda6029 / Wikimedia Commons, CC BY-SA 4.0