OSJ Ontake 100km Ultra Trail

Race completed

99.5 km Distance

3,395 m Climbing

10.0 Grit · Elite / extreme

35.7962° N, 137.5637° E © OpenFreeMap © OpenMapTiles Data from OpenStreetMap

What the course asks

Climbing rate 34 m / km Rolling. Moderate undulations. Requires consistent effort across varying grades.

Time limit 20 hours 12:04 min/km average. Generous. Walkable throughout for most of the field. More forgiving than 78% of 100K races. Measured against 203 races of the same distance. Cut-off calculator →

Field size ~879 Very large. Congested start, busy aid stations.

DUV results for the 2025 edition (99.5km) — finishers only. Starters are not published, so the field was at least this big and no finish rate can be given.

Typical conditions, July

Daytime high 24°C

Night low 16°C

Rainfall Wet — expect rain

Daylight 14 h 18 m of light

Regional 2001-2020 average for July — NASA POWER, grid elevation 1185 m. Not a forecast.

The Aid Station

Course-specific beta from the community

⛰️ terrain

This is a rolling course. Expect fast, runnable sections where rhythm is key.

By UltraHub Expert

👟 gear

With trail terrain, choose a shoe with moderate cushioning for optimal performance.

By UltraHub Expert

Gear for this race

Chosen for 100 km of trail with 3,395 m of ascent.

Trail Running Shoes 34 m of climb per kilometre — grip and rock protection before cushioning.
Race Nutrition Past 100 km the palate quits before the legs do — carry more than one flavour.
Hydration Vests Pole attachment and chest-strap stability on steep ground.
Trekking Poles 3,395 m of ascent to walk up.
Headlamps A 20 h limit puts you out there after dark.