I never did think of trying to sample caucasian women in Japan, largely because I found the Japanese girls beutiful, gracious and readily available, either through escort services or through the bars near Shinjuku. Maybe my experience was a little different since I was there for six months as the only gaijin working with about 2 dozen Japanese. They were so committed to making sure I enjoyed Tokyo that I never had a problems finding someone who knew the city well with whom to go out at night.
Most of the guys I know who worked as expats in Japan for far longer than I did really enjoyed themselves, and found the Japanese women delightful and anxious to get to know Westerners. I'm not dissing your experience. Just saying that there are lots of ways to enjoy the beauties of Tokyo.