Distance
Terrain
The Shimanto River Ultra Marathon Online Challenge asks runners to cover 100km on their own terms, wherever they happen to be, and to log the distance through the official challenge platform rather than gathering at a start line. The event borrows its name from the Shimanto River in Japan, often called the country's last clear stream, and it welcomes both runners who have taken on the real Shimanto River Ultra Marathon before and those who have only dreamed of it. Several scheduling variants are offered, running from a single month of training or racing up to a three month block, so participants can choose how much time they want for the distance. Every entry tier includes a T-shirt, and higher tiers add gifts such as Shimanto udon noodles, local bonito straw-seared tataki, Shimanto beef, Shimanto eel, or an original apparel set of cap, long-sleeve T-shirt, pants and hoodie.
Start / Finish
No fixed start line. The challenge is completed remotely, at a place and time of the participant's choosing, over the selected challenge period
No fixed finish line. Runners submit their completed 100km through the official challenge platform
What to bring
A smartphone on which the GPS training app TATTA can be downloaded (iOS 16+ / Android 10+)
What you get
A T-shirt is included with every entry tier
Choice of finisher gift depending on tier: Shimanto udon noodles or long-sleeve T-shirt, pole-caught local bonito straw-seared tataki, cap, pants, hoodie, Shimanto beef (sukiyaki-cut or yakiniku-cut), Shimanto eel, or an original apparel set of cap, long-sleeve T-shirt, pants and hoodie
On the day
Before you enter
Other questions
It is a virtual challenge rather than a mass-start race. Participants commit to covering 100km over a chosen period and submit their completed distance through the official challenge platform, running wherever they like. The event takes its name from the Shimanto River Ultra Marathon, a real ultra held beside Japan's last clear stream.
Anywhere you choose. There is no fixed course, no start line and no finish gantry, so runners can complete the distance on home roads, local trails, a treadmill or a mix of all three. That also means you arrange your own water, food and safety cover along the way.
Yes. The challenge is set up so that the distance is accumulated over your chosen period, whether that is one month, two months or three months. Rather than one long effort, most participants build the 100km out of a series of shorter runs.
The offering spans one month options such as the October Run, November Run, Training and Year-end blocks, two month variants split into Stage 1 and Stage 2, and the three month build. Shorter periods suit runners who want a focused block, while the three month version spreads the distance more gently.
Every tier includes a T-shirt. Above that, the fee rises depending on the finisher gift you pick: long-sleeve T-shirt or Shimanto udon noodles, or a choice of pole-caught local bonito straw-seared tataki, cap, pants or hoodie, or a premium tier with Shimanto beef, Shimanto eel or an original apparel set of cap, long-sleeve T-shirt, pants and hoodie.
Entry fee
Registration isn't open yet. We'll show pricing when the organiser confirms.Kiryu, Japan
Expected October 2027
Provisional date, around Oct 7Are you the organiser of Shimanto River Ultra Marathon Online Challenge [3-Month 100km]?
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