The Kumakogen tourism association gives the peak at Omogo-kei as early to mid-November. The same association puts the Ishizuchi Skyline, the road that climbs from the gorge entrance, at mid to late October. The road and the valley below it are a fortnight apart, and the reason is simply altitude.

Omogo-kei spreads across the southern foot of Mount Ishizuchi and is one of the larger gorges in Shikoku, designated a place of scenic beauty by the state. The water of the Omogo river runs clear with a green cast to it, and in November the red and yellow sit directly on top of that colour rather than beside it.

The gorge is unusually approachable for its scale. Paths have been made up through it, so this is a walk rather than a scramble, and the odd rock formations and stretches of river arrive at intervals rather than needing to be sought out. An afternoon covers the main routes at an easy pace.

It is fifty minutes by car from the Kumakogen town hall, on a road that goes steadily further into the mountains, and there is not much between. Winter closes the whole basin under snow; spring brings new growth and summer brings people into the river. November is the fortnight when the water colour and the leaf colour are both at full strength at once.