It's definitely Tohoku. Autumn foliage season for Tohoku normally starts mid to late Oct. For Kyushu, it doesn't start till early or even mid Nov.Popular sites for autumn foliage in Tohoku include Yama-dera, Ginzan Onsen, Naruko Gorge, Nyuto Onsen, Kaunodate, Hirosaki, Oirase Stream and Towada-ko.
For more references for autumn foliage in Tohoku:
http://www.rurubu.com/season/autumn/koyo/area.asp?area=...
http://kouyou.nihon-kankou.or.jp/list/result.php?m=1&c=...
http://www.mapple.net/sp_koyo/list.asp?AREA=2
http://www.walkerplus.com/koyo/tohoku/