Kozan Green Race (Trail)
20k, 10k, 5k, 3k, 1k
Date: September 27, 2015
Where: Noboribetsu Nature Center "Foresto"
Fee: At 2000 yen for adults, this is one of the cheapest races out there.
The trail looks like it is all dirt and gravel road.
Kozan means "mine".
It doesn't look like they will use any online entry sites for this. The Shikaoi Trail Run is the same. You have to send the money to them via bank transfer with your name, age, and race distance.
It looks like fun.
They have information on their website here: