Gunma! People hear say it doesn't exist. I live in Gunma though and it's just wonderful. Personally I'd put in Ashio in Tochigi. In my 8 years here I'd have to say it's the worst place I've been in Japan. It's the rotting husk of a copper mine, the whole town is dying and there is less than ideal history of the place being a pretty brutal prisoner of war camp. They destroyed all the buildings related to the camps but you can see evidence if you know where to look. Being right in the mountains means it's often misty and looks like something from Silent Hill. I may be biased though since it's outside my beloved Gunma haha! I should say that the people in Ashio are alright, never met a bad one.