Yes, Shikoku and Kyushu are both very pleasant from my experience. Shikoku felt the least visited. In Matsuyama, I saw only a handful of western tourists and even those were mostly blended families probably visiting relatives.

It was really pleasant. I keep trying to move farther off the beaten path on each trip.

In Beppu you’d mostly find Korean tourists who come by ferry, rather than the wrecking ball tokyo-osaka-kyoto tourists.