Subtle Signs

From Ginzan Onsen, an traditional hot spring town.

Visiting sento, public baths or onsen, hot springs is the favorite pastime of the Japanese. According to the survey conducted by Japanese tourism association, visiting Onsen has been the most popular activity upon travel for leisure consistently.
I believe there are not many places more suitable than such where you can see how people behave. Here in a typical Ryokan, Japanese traditional accommodations, would remind private bath users to place their sandals in front of the door as an indication that you are inside. There is a key but it is only a metal hook which does not quite serve the purpose. Ryokan knows that items like sandals are more obvious and natural ways to indicate that there is someone inside.
And for a public bath area, where you meet people naked, these baskets are here to indicate if there are people inside before you. Baskets are placed upside down by default in the area where you undress yourself; Once you get in, flip them back, put your clothes and towels. The flipped basket with the clothes inside will give the next customers how crowded or even whether there is anyone inside before you. And what is the impact of this? You will know whether you could go inside, just like in your home completely naked, or whether you should hide a few parts of yourself with a small towel, which you will use inside to wash yourself with.

REPLY))
It must be pretty popular, because there is “almost” not an anime in “daily life” genre without appearance of onsen.