Belton wrote:Nor do I think Japanese at the time were prudish enough to wear a weird cotton gown in the sento. (Don't want nudity put your scene elsewhere)
There are some onsen where you are forbidden to enter naked. And not for prudish reasons, but for religious reasons. There is one on Sakurajima (the active volcano in Kagoshima). It's a kon'yoku onsen (kon'yoku = men and women bathing together), which usually implies nudity, but because the spring is sacred (Shinto?) ground, bathers have to enter in a heavy cotton yukata.
So the MemGei scene could be accurate...
You're right that it's unlikely though. I've been to tons of onsen, and that's the only one where nudity was forbidden.
P.S. I think this movie stinks.