6. Wrong Dressing RoomIt's quite possible to enter the wrong dressing room if you're not paying attention.
Usually, the woman's curtain is red and the men's curtain is blue (but not always). Usually, the curtains use the kanji "女" for women and "男" for men (but not always). The kanji on the curtains are often stylized (difficult to read).
The men's and women's baths are often rotated during the day or several times a week (by switching the curtains).
5. ShoesYou're expected to remove your shoes at the entrance to most onsen. Walking straight in with your shoes on is a major faux pas.
4. Forgetting Your Little TowelJapanese onsen aren't nudist resorts. You're expected to show a little modesty where possible. Most people carry a small towel in the bath with them. This towel is used to wash. It shouldn't enter the onsen bath itself. It's common to place the towel on your head when you're in the bath.
Most people use the little towel for modesty when getting in and out of the bath.
If you forget your little towel it's not the end of the world. However, you might feel embarrassed if everyone else has one.
3. Forgetting to WashOnsen is often not chlorinated. It's important to health and cleanliness that everyone wash before getting into the shared bath.
If you forget this step people will notice.
2. Bathroom SlippersIf you go to the bathroom in the dressing room — bathroom slippers will be provided. If you forget to take these off when you return to the dressing room — people will be shocked.
1. The Worst ThingMost onsen require nudity and have separated baths for men and women. Some onsen are mixed sex and require bathing suits.
The most embarrassing thing that can happen — coming out of the dressing room nude at an onsen that requires a bathing suit.