I was never at Camp Kisner, but I did spend about 2 months on Kadena Air Force Base and I think it's all one base. The gym there is pretty nice.
I went UDP to Iwakuni twice so I was there about 14 months in total. We use to joke, you'll either become a gym rat, a drunk, or you'll find Jesus while in Japan. It's the truth too in my experience.
A couple of pieces of advice from a former Sgt regarding your time overseas. You're going to have a lot of time to yourself over there and it's the best time you'll ever have to make progress in the gym, bar none. Take advantage of that time. Don't spend every Friday night out in town (There's the main strip everyone goes to, I forget what it's called. Gate 2 street maybe). Enjoy yourself a few times, but not every week. You will see a lot of Devil Dogs waste all of their time and money on beer and strippers. It's a total waste. Keep your head down, PT your ass off, get your MCI's done, and progress in rank. Don't be stupid while you're there like a lot of Marines.
For the love of God, don't buy a car while you're there. If you're going to buy a car take advantage of the deferral program. I can't remember what it's called, but basically, you will pay a certain amount per paycheck while you're there and you'll get a new car when you get back to the states. Just check the px for details.
Speaking of money, this is a great opportunity to save it. I would suggest creating a savings account that isn't easily accessible (I used INGdirect now Capital360 while I was there) and splitting your direct deposit so a portion goes to that account. Then forget about it. Learn to live off the rest. You'll thank me when you get back to the states or not, it's your money.
If you can, find a Mongolian BBQ place preferably on base. We had one in Kuni where you'd load a bowl with all of the meat you wanted, weighed it, and paid a few bucks per pound. Then you added as much rice as would fit for free. It's a very cheap way to eat a ton of delicious food. I usually got 4 meals or so for about $15 and it was very good.
Don't waste your money on stupid shit. Instead, see as much of the island as you can.You can drink case after case of Bud Light when you get back to the states, but you'll probably never go back to Japan in your life.
Go UDP if you can. Cobra Gold is going on right now, I believe, in Thailand. Cope Tiger, which I was a part of in 2006, is another opportunity to see Thailand. I would highly recommend going to Thailand if you can. It's cheap, the people are extremely nice, and it's really something else. They serve some of the best fish you'll ever have.
Pattaya Beach Thailand (which you may or may not be able to visit during Cope Tiger, I lucked out) is like Adult Disney World. You'll see some shit there...
There are usually opportunities to go to Australia and South Korea as well. It's basically free travel, take advantage of it if you can.
Lastly, don't forget you represent the Unites States Marine Corps while you are there.