Although percentage-wise and historically many more men wear fundoshi than women, fundoshi are gaining ground as women's undergarments too (especially etchū-style, and I can understand why with their cool, light comfort). Rokushaku-style or a variation of it has been used by female pearl divers ("ama") for generations. Plus, there has always been a healthy fetish market for women in fundoshi. While the male anatomy definitely provides more of an anchor-point for the front pouch/basket of the fundoshi, I think many of these ladies wear their rokushaku fundoshi quite well, and I applaud their bravery and poise.
We could devote an entire future post to the etchū-fundoshi revolution happening for Japanese women. High-end department stores offer matched sets of fundoshi and brassieres with more feminine fabrics and patterns.
Rokushaku fundoshi certainly becomes highly eroticized in this context, highlighting its potential for similar display on the male anatomy, and while I do feel that fundoshi is best on a man, I'm not selfish enough or hidebound enough to deny any woman the opportunity to enjoy this classic garment. Women looking for something to wear under clothing should check out etchū fundoshi (or even mokko-style), women who want to make a statement at the beach or surprise their lover would certainly score major style points in rokushaku fundoshi!