-The DO's and DON'Ts of a Mixed Onsen -
Onsens, or hot spring baths / spas, are a fabulous part of Japanese culture that can only be experienced and not described, so I'll only say that Aomori ken has some of the best onsens around. Some are urban and modern, others are rustic and isolated. Some are segregated and others mixed. While seemingly more terrifying than the summer "bathing suit on the beach" season, I guarantee that at some point most of you will find yourself soaking up onsen life buck naked and in the company of members of the opposite sex. Do not panic! There are rules for MIXED onsen conduct and etiquette to guide you. It's usually best to observe how Japanese folks behave and follow their lead. Generally speaking, Japanese folks:
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DO:
Bring an onsen modesty towel. There may seem too tiny to actually be modest but they are essential to cover up those areas that require the most modesty.
Use the modesty towel when walking around the pool area or setting on the side. It isn't necessary to use one when actually sitting in the pool. Put it to the side or fold it and put it on your head. (Trust me, that won't sound or look so ridiculous after you've been here a while.)*
Behave respectfully and maturely. No staring, ogling or "woohooing" fellow onsenners.
Sit quietly and just relax. No splashing, swimming, frolicking, or flashing the other onsenners. There is also no physical contact in an onsen. Public displays of affection are not welcome in Japan as a rule and the onsen is no different.
Use the changing areas provided for removal or putting on of clothing.
Wait ouside communal changing rooms when members of the opposite sex are using them. No changing together.
Approach foreigners to gasp at freckles, ask how far freckles go down, compare breast / genitalia size, ask for photos with foreigner standing only in knee high water, ask what their grandmothers look like... "yes, well" you aren't actually required to do that and it would most assuredly be greatly appreciated if you refrained.
The big DO NOT for all onsens, mixed or otherwise is, of course, never bring any shampoo, soap or other bath products into an onsen. All showering, shampooing and rinsing must be done outside of the hot spring pool.
*please note that women are free to wrap themselves in full size towels which can be worn into the pool and removed or kept on, as you like. I haven't seen many Japanese women in mixed onsens and those I did see tended to favour the biggest towel but either towel size is appropriate. (and despite what you might think, you can find very large towels here, if needed-ed.)
Other considerations just for the uninitiated foreigner:
Don't sit too long your first few times onsenning. Every few minutes, sit to the side. You may not realize the effect the heat from the onsen has on you until it's too late and you've fainted. The water is usually about 35-45 degrees Celsius. Many a JET has succumbed.
Do bring bottled water to re-hydrate. Very useful to prevent fainting as well as to revive you if you should pass out. Don't panic though, it isn't as if JETs are dropping like flies. It's just something to be aware of.
So there you have the basic rules of mixed onsenning. Some JETs may tell you they've seen many Japanese folks breaking these rules and no doubt they have. All cultures have rude people who behave inappropriately. You may also see many foreigners who ignore these rules and that is of course, up to them. We all have different views on what modesty is. However, I ask you to remember that this is Japan, these are their onsens and they are an integral part of daily life for the Japanese. It is their idea of modesty that counts. The presence of foreigners can be unnerving enough but rude and inappropriate behaviour can cause Japanese folks to leave onsens when foreigners arrive or discourage them from even entering the pool. There are some onsens in other kens that have "No Foreigners" policies due to repeated inappropriate behavior. Bad behaviour can also result in unwanted attention and rudeness from Japanese folks who feel that the rules can be broken due to our own lack of manners. This is rare and 95% of the conversations I had with Japanese people, naked in an onsen, have been highly entertaining. However, being foreign will get us enough attention I guarantee. So please, for the sake of everyone who loves an onsen, follow the rules and really experience one of the best parts of life in Japan. Oh yeah, and bring moisturizer. Onsens give new meaning to "wrinkly as a prune"
as found on :
The DO's and DON'Ts of a Mixed Onsen