Please recommend some small Japanese cities

1. I'd prefer it if it's not too rural (at least a city-level area comparable to a 'si' in Korea)
2. I'd like it to be close to an airport (it doesn't have to be on the scale of Fukuoka, but as long as it's not too far, it's okay)
3. I'd prefer if the cost of living is relatively low
I would appreciate the expert advice of you travel pros
(Please refrain from leaving comments like 'Just go to Tokyo or Osaka...')