Whether it's a bright, modern place in Omotesando with fizzy water and fancy soap or a creaky neighborhood bath with a coin-operated hairdryer that's been bolted to the floor since the 1960s, all public baths cost ¥450.
The Tokyo Sento Association is redoubling efforts to make them foreigner friendly ahead of the Olympics by posting etiquette and instruction cards in four languages.
7. That word you keep hearing is 'welcome'
After a few days in Tokyo, you might find yourself asking, "What's that thing they always say when I walk in?"
Whether it's sweaty, aproned guys shouting in unison as you walk into an izakaya (lively restaurants that serve alcohol with lots of small dishes) or one perfectly coiffed woman murmuring as you enter the hush of a small boutique, they're saying the same thing: "Irasshaimase."
It's a polite way of saying "welcome."
Although your instinct may be to reply -- "Thank you?" "Hello?" -- locals insist no response is required. A friendly little bow in response doesn't hurt, though.
8. The sushi really is that good
The famous tuna auction at Tsukiji market starts just after 5 a.m., but the day's 120 free tickets are often all snapped up as early as 4.
Whether you get to the auction or not, the market and surrounding shops will be springing to life around that time -- it's the best place to enjoy an early morning plate of the freshest sushi you've ever tasted.
You need not be there that early, but many of the hundreds of shops start to close by 1 p.m.
Visit and you, too, will be one of those insufferable diners who can't eat sushi back home without saying, "It's good, but it's nothing like the maguro I had in Japan."
But hurry -- the legendary market is set to close at the end of 2013. A new facility will open a few kilometers away in 2014.
More: Iconic fish market to close
9. Free WiFi is rare
While the number of places that have free and simple WiFi in Japan is increasing, access isn't something you can count on.
Signs everywhere announce free WiFi -- if you already have a contract with the provider.
Even places like Starbucks that have relatively accessible free WiFi require you to create an account in advance.
Instead of renting a SIM card, many travelers find that renting a pocket WiFi at the airport to use with their own smartphones is the best way to get online.
10. Bacon turns up everywhere
Japan has a long tradition of Buddhist vegetarian cuisine called shojin ryori. It is painstakingly prepared and served on fine lacquerware and ceramics.
It's worth experiencing (Michelin-starred Itosho is outstanding) and guaranteed to be vegetarian, but it's expensive and a time-consuming affair.
For a quick veggie meal, you usually have to be vigilant. A "vegetable sandwich" may have a sneaky slice of ham in it, and pasta with "no meat" could be studded with chunks of bacon. "Meat" tends to mean "beef."
Running down a list of every animal product that you'd like to avoid is the only way to be sure. And your potato salad might still come with bacon.
11. Clear umbrellas are the best umbrellas
Into every vacation a little rain must fall.
If you're in Japan when it does, lucky you -- it's a perfect opportunity to pick up a clear umbrella.
It's such a simple innovation, you wonder why they haven't caught on elsewhere.
Once the first drops of rain hit the street, you'll find them everywhere.
Convenience stores will put their stock by the door. One costs between ¥300 and ¥500.
The clerk will offer to unwrap it for you if you're using it right away. Hold on tightly, but let go lightly; umbrellas are the one item that's frequently stolen in Tokyo.
If yours disappears, consider it a rite of passage.