Hiratsuka, Kanagawa Pref., Japan · Monday, September 21, 2026

Timed 6 hours

Shonan Int. Relay Marathon 6 hour Run

Race completed

not publishedn/a Distance

not publishedn/a Climbing

not publishedn/a Grit

We hold no course length for this race — a timed or backyard event is measured by the clock, not the kilometre — so there is no Grit score to give you.

35.3351° N, 139.3494° E © OpenFreeMap © OpenMapTiles Data from OpenStreetMap

What the course asks

Field size ~17 Tiny. You will run alone for most of it.

DUV results for the 2025 edition (6h) — ranked runners only. Starters are not published, so the field was at least this big and no finish rate can be given.

Typical conditions, September

Daytime high 26°C

Night low 18°C

Rainfall Wet — expect rain

Daylight 12 h 14 m of light

Regional 2001-2020 average for September — NASA POWER, grid elevation 233 m. Not a forecast.

Results history

Year	Race	Finishers	Men's winner	Women's winner
2025	6h	17	Ryo Abiko · 70.659 km	Manami Mokudai · 58.595 km
2019	6h	36	Hidetsugu Arai · 83.040 km	Chiaki Ono · 67.470 km
2018	6h	29	Hidetsugu Arai · 81.300 km	Naoko Huzieda · 51.900 km
2017	6h	30	Hiroki Arai · 81.310 km	Aya Doi · 65.740 km
2016	6h	47	Hideaki Yamauchi · 88.230 km	Kayoko Kato · 65.740 km
2015	6h	64	Hideaki Yamauchi · 83.040 km	Kayoko Kato · 65.740 km
2014	6h	64	Hideaki Yamauchi · 84.770 km	Atsuko Sato · 64.010 km
2013	6h	92	Hideaki Yamauchi · 79.580 km	Kazuha Matsui · 65.740 km
2012	6h	81	Hideaki Yamauchi · 81.310 km	Maki Niikura · 62.280 km
2011	6h	107	Hiroki Arai · 79.580 km	Josephine Josephine · 64.010 km

The field shrank 53% between 2019 (36) and 2025 (17). 18% of the 2025 field were women.

DUV results for the 2025 edition (6h) — ranked runners only. Starters are not published, so the field was at least this big and no finish rate can be given.

Course notes

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

Gear for this race

Chosen for this trail race.

Trail Running Shoes Cushioning on trail that is still there in the last quarter.
Race Nutrition Self-supported fuelling between aid stations.
Hydration Vests Flask capacity without the bounce.
GPS Watches Battery life first — an ultra outlasts most full-GPS modes.

Brooks

Cascadia 18

Versatile trail shoe with BioMoGo DNA cushioning and TrailTack rubber outsole.

$140 ★★★★★ 4.5

Asics

Endurance Fuel

All-in-one calorie and electrolyte drink mix. 200 calories per serving.

$25 ★★★★★ 4.8

Nathan

VaporKrar 12L

12L race vest co-designed with ultra champion Rob Krar, with insulated bladder pocket.

$170 ★★★★★ 4.6

Garmin

Enduro 3

Ultra-endurance GPS watch with solar charging and 300+ hour battery in GPS mode.

$900 ★★★★★ 4.8

All gear guides →

Overview

The Shonan Int. Relay Marathon 6 hour Run challenged participants to accumulate as much mileage as possible against an unyielding 6-hour time limit rather than chasing a fixed finish line. Staged by Runners Wellness Inc. in Hiratsuka, Kanagawa Pref., Japan, the event held 10 editions from its inaugural running in 2011 through 2025.

Because competitors ran continuously on a paved circuit measuring under 5 kilometers, pacing required strict clock management over a recurring circuit where dropouts and support stops were always close at hand. The 2025 edition saw 17 runners reach the final whistle, marking a low-density field where participants rarely had to navigate congestion despite the tight loop structure.

Similar races

Other trail ultras of the same format.