I'm origionally from Washington State (US) and have been in Japan off and on since 1997.
So far I love Shikoku. I know of the valley you mentioned, but have yet to get there. If you look in the middle of the penninsula-like far southwestern corner of Kochi-ken, thats me! The only catch is that it takes soooooo long to get anywhere. The scenic beauty makes up for it, but Kochi City is four hours by car, two by train. If I want to get to Honshu (Okayama)by train, it takes nearly five, yes, five, hours and costs as much as the Shinkansen from Hiroshima to Tokyo. The trains around here are gas powered, not electric. Inaka da yo! All said, I wouldn't trade it for anything.