I spent close to 3 years in Japan. My first few months there, I was very intimidated by them. I was pretty AFC then and catered to them. Bad move for american girls... Even worse for Japanese girls.
As time progressed, I figured them out to the point of where I would meet them on a Thursday night, and by Friday night, they were in my bed.
My advice not only for them, but for all women is this:
Don't be afraid. Talk to them. Show them that you're interested. When you find one at a particular spot and you guys hit it off nicely, stick with her. They will be quick to call you a playboy if you wander.
I usually frequent spots regularly everywhere I go. If you do this there and you're cool, the japanese guys will befriend you and take you to those cool spots where americans are off limits. They love american women, so if you can introduce them to your friends then you're golden.
Overall, have fun! Gambate ne!