Iki, Nagasaki Pref., Japan · Saturday, October 17, 2026

Fixed Distance 100K

Iki 100 Km Ultra Marathon

Race completed

100 km Distance

not publishedn/a Climbing

5.0 est Grit · Challenging

Calculated from 100 km alone — the organiser has not published an elevation profile. Read 5.0 as a floor, not a verdict.

33.7501° N, 129.6913° E © OpenFreeMap © OpenMapTiles Data from OpenStreetMap

What the course asks

Time limit 14 hours 8:24 min/km average. Tight. Sustained running. Long aid-station stops will cost you. Climbing is unpublished, so this pace is a ceiling on the effort, not a measure of it. Tighter than 81% of 100K races. Measured against 226 races of the same distance. Cut-off calculator →

Field size ~376 Large. Rarely out of sight of another runner.

DUV results for the 2025 edition (100km) — finishers only. Starters are not published, so the field was at least this big and no finish rate can be given.

Typical conditions, October

Daytime high 22°C

Night low 20°C

Rainfall Showers likely

Daylight 11 h 20 m of light

Regional 2001-2020 average for October — NASA POWER, grid elevation 4 m. Not a forecast.

Results history

Year	Race	Finishers	Men's winner	Women's winner
2025	100km	376	Takahiro Tomoguchi · 06:53:09	Tomoko Fujioka · 09:16:10
2024	100km	301	Takahiro Tomoguchi · 07:15:10	Mayuko (Myako) Tsuji · 09:49:14
2023	100km	335	Fumiya Imamura · 07:36:05	Mayuko (Myako) Tsuji · 09:16:00
2022	100km	198	Ryo Obayashi · 07:49:12	Mari Ueki · 09:55:22
2019	100km	282	Morimichi Iihoshi · 07:40:52	Konoka Azumi · 08:12:29
2018	100km	326	Kazuaki Kawashita · 07:24:37	Mika Higashi · 09:38:55
2017	100km	251	Yuichi Mizuta · 08:16:20	Yuko Nakashima · 10:23:20
2016	100km	165	Toshiro Naraki · 07:52:56	Eiko Matsuda · 10:10:17

The field grew 25% between 2024 (301) and 2025 (376). 15% of the 2025 field were women.

DUV results for the 2025 edition (100km) — finishers 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.
nutrition For 100km+ efforts, prioritize real food at aid stations to prevent palate fatigue.

Gear for this race

Chosen for 100 km of trail.

Trail Running Shoes 100 km of trail — cushioning that is still there in the last quarter.
Race Nutrition Past 100 km the palate quits before the legs do — carry more than one flavour.
Hydration Vests Flask capacity for 100 km, without the bounce.
Headlamps A 14 h limit puts you out there after dark.
Accessories Chafe and blisters end more 100 km races than fitness does.

La Sportiva

Prodigio Pro

RunRepeat found the La Sportiva Prodigio Pro to have a secure, locked-in fit due to its premium upper, and also praised the shoe's energetic ride, particularly…

$225 ★★★★★ 4.6

Asics

Trabuco Max 3

★★★★★ 4.6

Maurten

Gel 100

Hydrogel technology for 25g carbs per gel with minimal GI distress.

$3.5 ★★★★★ 4.7

Salomon

ADV Skin 12

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

$180 ★★★★★ 4.8

Petzl

NAO RL

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

$150 ★★★★★ 4.7

Squirrel's Nut Butter

Anti-Chafe Balm

All-natural anti-chafe balm. Essential for 100+ mile races.

$12 ★★★★★ 4.8

All gear guides →

Overview

The Iki 100 Km Ultra Marathon, a 100k road race, will be held on October 17, 2026, in Iki, Nagasaki Pref., Japan. With 376 finishers at the 2025 edition, this race has a field size bigger than 91% of 100k races.

The 14-hour time limit for this 100k race results in a cutoff tighter than 81% of 100k cut-offs, allowing for a pace of 8.4 minutes per kilometer. This may require runners to maintain a consistent effort throughout the course, leaving less margin for slower sections compared to 19% of its peers.

Similar races

Other 100K trail ultras, closest in distance first.