I'm planning on going to a mixed gender onsen (konyoku), and one place suggested to me in Nyuto onsen village, Tohoku, has a male only section, a female only section, and a mixed section. If I'm by myself (as opposed to being part of a mixed sex group), am I going to raise eyebrows if I choose the mixed section?
One ojiisan (old man) told me that obaasan (old women) are the only women who bathe without a towel in mixed onsen nowadays. Maybe that means I wouldn't be accused of having bad motives in choosing a mixed onsen, unless a fetish for old women exists in Japan.
Also, I've heard that mixed onsen are becoming increasingly rare in Japan, mainly confined to conservative rural areas (perhaps non-tourist oriented onsen?). Why is this happening? Are western influences to blame? (I asked the ojiisan about it, and he didn't know either)