Japan
Maybe doesn't have the paddling quality for those on a paddling-only-mission, but is a interesting destination culturally. Rivers are generally short and pool-drop, with a high proportion of dam-release runs. Dave Goadby characterised the rivers as concrete, "even down in the bottom of deep gorges there's pipework and construction stuff".
When to go
July-August.
How to get there
Fly into Tokyo.
Transport
You will need your own vehicle, but the infrastructure is very good and all runs are close to or directly accessible from a road.