Erik: Right. There are also stories that people don't wear underwear under their gi... again because that was originally the underwear, I suspect.

Clare: Well, it's also very similar to what you do wear under a kimono, a nagajuban. At my wife's kimono school, they are strictly forbidden to leave the classroom without putting a kimono over the nagajuban, even though there are about three layers underneath it. (Maybe only two; padding and normal underwear.) How's the fifth paragraph now?

Gillsing: Right. Even more so because at a lot of Japanese hotels you are allowed, even supposed, to walk around in the yukata. This is particularly true at traditional ryokan. I've been to one where I think everyone wore the yukata nearly all the time around the place, including outside in the grounds.

One consequence of all this is that, if you go back into costume history, miko are always walking around in their underwear. The white kimono and red hakama were, back in the Heian period, underwear. Of course, the modern formal kimono was underwear back then as well.