End of November - early December is really late... You might probably have a chance in the Chugoku and Kyushu part of Japan, but of course it is difficult to predict how things will be.
If you select the second link : http://www.walkerplus.com/koyo/
1) Click on the map on the area you are interested in
2) Choose the period you will be traveling in the "見ごろ検索" list (left menu), you can select the date with "11月下旬" (last 10 days of November) and "12月上旬" (first 10 days of December).
3) You will get a list of the most interesting spots in that area (if you can not exactly understand the location, just copy the address in googlemap, it will locate the spot for you).
Hope this helps,