Non-standard Japan cycling routes.

I've gone on two tours of Japan and I'm thinking about heading out on another. Tentative plan right now is to fly to Sapporo, ride to Wakkanai, then head south down to Kyushu again, riding the east coast initially down to Tokyo then crossing over to the west. Love to hear suggestions for places I haven't been yet, maybe some tips for getting up into the mountains more. Trip reports would be great!