The Mount Noro Speed Park (野呂山スピードパーク) was a race circuit in Kure, Hiroshima, Hiroshima Prefecture, Japan, active between 1970 and 1974.
This GR track is based on an rFactor version by soramame6r4.
I could only find 1 photo of the real track and it appears they bulldozed the forest, built the track and left it at that.
The track has 2 alternate routes but there really wasn't room to do them on the GR track.