I am biased towards the Kanagawa Prefecture. My Inlaws live in Hadano, I used to live in Zama, and most of my old hangouts are between Zama and Atsugi.
That said, Kanagawa is a pretty nice place IMO. There is plenty to do (as with most places in Japan) and it is relatively close to Tokyo.
The cost of living is significantly less than Tokyo too. Of course, I can just stay at my Inlaws house and enjoy this view
