Tsunan, Niigata Pref., Japan · Sunday, July 5, 2026

Fixed Distance 50K

Naeba-Sanroku Geopark Tsunan Ultramarathon 48K

Race completed

48 km Distance

2,800 m Climbing

6.6 Grit · Hardcore

37.0143° N, 138.6525° E © OpenFreeMap © OpenMapTiles Data from OpenStreetMap

What the course asks

Climbing rate 58 m / km Mountain. Significant climbing. Steep sections will require power hiking.

Time limit 15 hours 18:45 min/km average. Generous. Walkable throughout for most of the field. Among the most forgiving 50K cut-offs we track. Measured against 1063 races of the same distance. Cut-off calculator →

Field size ~72 Mid-sized. Company early, well spread out by halfway.

DUV results for the 2026 edition (48km) — 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 26°C

Night low 17°C

Rainfall Wet — expect rain

Daylight 14 h 38 m of light

Regional 2001-2020 average for July — NASA POWER, grid elevation 784 m. Not a forecast.

Results history

Year	Race	Finishers	Men's winner	Women's winner
2026	48km	72	Ken Yamanouchi · 03:22:25	Shinobu Tago · 04:34:09
2025	48km	60	Kazuki Takamura · 03:58:42	Maho Suzuki · 04:59:52
2024	48km	29	Yuu Kuwabara · 04:05:32	Tomoko Matsumoto · 06:01:49

The field grew 20% between 2025 (60) and 2026 (72). 32% of the 2026 field were women.

DUV results for the 2026 edition (48km) — 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 mountain course. Poles are highly recommended for the sustained climbs.
gear With road terrain, choose a shoe with moderate cushioning for optimal performance.

Gear for this race

Chosen for 48 km of road with 2,800 m of ascent.

Trail Running Shoes 58 m of climb per kilometre — grip and rock protection before cushioning.
Race Nutrition 48 km of self-supported fuelling between aid stations.
Hydration Vests Pole attachment and chest-strap stability on steep ground.
Trekking Poles 2,800 m of ascent to walk up.
Headlamps A 15 h limit puts you out there after dark.

Salomon

Sense Ride 5

RunRepeat found the Salomon Sense Ride 5 to have immaculate lockdown and a smooth and stable ride, making it confident on moderate trails and steep downhills. I…

★★★★★ 4.5

Adidas

Adizero Evo SL

RunRepeat found the Adidas Adizero Evo SL to be lightweight and well-cushioned, with a 100% Lightstrike Pro midsole and world-class Continental outsole. irunfar…

★★★★★ 4.7

Skratch Labs

Sport Hydration Mix

Clean electrolyte drink mix with real fruit flavor. Low sugar.

$20 ★★★★★ 4.5

Naked

Running Band

Minimalist waist-mounted running band. Ultra-light alternative to a vest for shorter races.

$60 ★★★★☆ 4.3

Black Diamond

Distance FLZ

Lightweight folding trekking poles with FlickLock Z adjustment. 340g per pole.

$170 ★★★★★ 4.7

Petzl

NAO RL

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

$150 ★★★★★ 4.7

All gear guides →

Overview

The Naeba-Sanroku Geopark Tsunan Ultramarathon 48K was a road race that took place in Tsunan, Niigata Pref., Japan, in July. This 48-kilometer event had 2800 meters of elevation gain, which meant 58 meters of climb per kilometer.

With a time limit of 15 hours, the event had a cutoff pace of 18.8 minutes per kilometer, which was more generous than 93% of 50k cut-offs. The field size of 72 finishers in its latest edition was bigger than 70% of 50k fields and smaller than 30%.

Organised by Sports Aid Japan, the race was held 3 times between 2024 and 2026.

Similar races

Other 50K road ultras, closest in distance first.