One of my favorite threads is the girls in the Japanese onsen..
https://forum.oneclickchicks.com/showthread.php?t=86156
Here are a few onsen stories....
1. Japan - Girl goes to onsen with mixed group of friends. Luckily it had a mixed pool.
hxxp://senseiaoona.livejournal.com/31155.html
2. Japan - Another mixed onsen story.
hxxp://sarahjapan.blogspot.com/2005/02/big-birthday-surprise.html
3. Japan - She did her best to maintain her modesty in the mixed bath.
hxxp://karenregn.com/2010/05/running-bare-at-minakami/
4. Japan - Two girls go to mixed onsen. A Japanese man offers to be their guide and take them to more. Wonder what his motive was. There are some pictures of the girls in the water, but you can't see anything.
hxxp://www.travelpod.com/travel-blog-entries/brianneinjapan/japan-2006/1203716700/tpod.html#ENTRY_LIST
5. Japan - Mixed group in the onsen.
hxxp://www.getjealous.com/getjealous.php?action=showdiaryentry&diary_id=6159 21&go=daoilee&PHPSESSID=33l68424gnv5fbclvpvkf2ofg 1
Includes picture of group in mud bath.
hxxp://www.getjealous.com/daoilee/photo/6577385/team-wild-mud-onsen.html