I am assuming that you are in the military? I lived in Sasebo 12 years ago and it was more of a family oriented place when I was there. If you are married it’s the idea place to be there are a lot of family things to do. If you are single you may want to travel to Nagasaki, Fukuoka, or Osaka to have fun. You can rent a car so you don’t have to pay for all those toll roads, which can be quite expensive. If you are in to sports there are a lot of activates to keep you busy with the artificial turf fields that they have there.
I currently live in Yokosuka, which is near Tokyo. I suggest if you have time try and visit Tokyo. Here they have most advance subway system in the world so you can get to anywhere you want to by train. I suggest the New Sanno Hotel, which is for military members and their families. It’s a four star hotel in the middle of the Roppongi district which is downtown Tokyo. You can catch the Shinkansen from Osaka which is cheaper and faster than catching a plane. The best of luck to you .