Otaki, Nagano Pref., Japan · Sunday, July 19, 2026

Fixed Distance 100K

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. Comfortable. Room to walk the climbs and stop at aid. More forgiving than 75% of 100K races. Measured against 226 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.

Results history

Year	Race	Finishers	Men's winner	Women's winner
2025	99.5km	879	Yutaro Yokouchi · 08:12:25	Shiori Kato · 09:52:50
2024	109.2km	915	Yuta Onodera · 09:23:20	Natsuki Sakai · 12:17:48
2023	109.2km	755	Fumio Shimura · 09:47:48	Izumi Tomizawa · 12:17:11
2022	106.5km	785	Hajime Mamba · 08:58:38	Ayako Yasuda · 11:40:38
2019	100km	842	Yutaro Yokouchi · 08:41:18	Kaori Asahara · 11:23:08
2017	100km	866	Masanori Makino · 08:17:46	Makiko Nakamura · 10:32:52
2016	100km	855	Takeshi Noda · 09:29:49	Yukie Kimpara · 11:06:44
2015	100km	707	Yoshikazu Hara · 08:25:49	Hitomi Ogawa · 11:22:34
2014	100km	763	Hironori Tasaka · 08:59:29	Kyoko Otsuka · 11:53:29
2013	100km	725	Tetsuo Watanabe · 08:24:20	Mikie Sakane · 10:04:19

The field has held steady: 915 in 2024, 879 in 2025. 15% of the 2025 field were women.

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.

Course notes

terrain This is a rolling course. Expect fast, runnable sections where rhythm is key.
gear With trail terrain, choose a shoe with moderate cushioning for optimal performance.

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.

Adidas

Terrex Agravic Speed Ultra

RunRepeat found the Adidas Terrex Agravic Speed Ultra to be perfect for midfoot and forefoot strikers, while iRunFar noted that the shoe feels incredibly effici…

★★★★★ 4.5

Asics

Trabuco Max 2

★★★★★ 4.7

Spring Energy

Awesome Sauce

Real food gel with 180 calories. Rice-based with natural flavors.

$4 ★★★★★ 4.6

Salomon

ADV Skin 12

Industry-standard 12L race vest with front flask pockets and minimal bounce.

$180 ★★★★★ 4.8

LEKI

Ultratrail FX.One

Ultra-light carbon folding poles (135g each) designed for mountain ultra racing.

$200 ★★★★★ 4.6

Petzl

NAO RL

1500-lumen reactive lighting headlamp with 15-hour runtime. Automatic brightness adjustment.

$150 ★★★★★ 4.7

All gear guides →

Overview

The OSJ Ontake 100km Ultra Trail is a 99.5 km trail race with 3395 m of elevation gain, held in Otaki, Nagano Pref., Japan, on July 19, 2026. This race has been run 10 times since 2013, with the latest edition in 2025 seeing 879 finishers.

This race has a bigger field than 97% of 100k races. The 20-hour cut-off is more generous than 75% of 100k races, allowing for a 12.1 minutes per km pace. The course climbs 34.1 meters per kilometer.

Similar races

Other 100K trail ultras, closest in distance first.