Shimanto River Ultra Marathon Online Challenge Japan 2026: Year-end 1-Month 100K

Shimanto River Ultra Marathon's Year-end 1-Month Online Challenge is the December-only virtual 100 km round, separate from ARC's existing November 100K draft.

Complete 100 km cumulatively

Run at least 100 km between 1 and 31 December 2026 using TATTA. Multiple runs may be combined. Manual distance entry is generally not accepted.

Participants must reside in Japan, have a compatible smartphone and be able to use TATTA. No age restriction is published.

Registration and package choices

Registration closes 26 November 2026 at 23:59 JST. Four package tiers are published, all plus 6% RUNNET handling:

• JPY4,990: original event T-shirt
• JPY6,990: Shimanto udon or original long-sleeve shirt
• JPY8,990: straw-seared bonito or event cap / shorts / hoodie
• JPY12,990: Shimanto beef, Shimanto eel, or an original apparel set

Verified finishers receive the current challenge finisher medal.

Practical notes

There is no participant insurance, baggage service or physical-race support. This is a self-directed virtual challenge, not access to the physical Shimanto River Ultra Marathon course.

Credibility

RUNNET and the official Shimanto online-challenge site publish matching dates, registration details, TATTA rules and package structure. R-bies Sports Foundation is the named organiser, providing a strong institutional source chain.