Onsen is one of my favorite, so whenever I had the opportunities I would spend an hour soaking in onsen. There is a couple of sento or bath houses in downtown Tokyo that are wonderful.
To visit sento, you also need to get armed with an open mind and some Japanese yen. Optionally you should bring a small towel for scrubbing/drying off, a quality body lotion and soap, with a bottle of water to keep you dehydrated. However, all the optional items can be bought or rented at inexpensive price. Sometimes a public bath chooses a day in a week to be closed for regular cleaning and maintenance, so it is good to check which day it is, commonly Monday/Tuesday/Wednesday. Public bath normally operates from 3pm onwards through midnight, but some public bath is open a shorter during in AM for a morning soak.
A sento commonly provides small and medium towel rentals, as well as soap and shampoos/conditioner either complimentary or at sale. Normally there is also a laundry shop next to it.
You approach sento, remove your shoes in one of the shoes locker, keep the key, and purchase a ticket on vending machine. Then, hand your ticket to the cashier to obtain entry.
The cashier is located at a lobby or bathing entrance area that generally also has multiple items available for purchase such as travel size soap, shampoo, conditioner, souvenir towel. It will have a drink vending machine that has mineral water and milk.
Notice the entrance to women and men changing area, and do watch out to enter the right area! There is often a smaller red and blue banner over the entrance of each area respectively.
At the changing area, remove all article of clothing and store them in the lockers provided. The lockers would use coins that is either refundable or costing 100yen per use. There is also a toilet which you can use to relieve yourself prior to entering the bathing area. Slippers are always provided for you to wear while using the toilet.
With a small towel and bottle of water, enter the bathing area and start washing yourself. The courtesy is to cleanse yourself and shower as well as cleanup the area afterwards without hogging a seat. From health standpoint, showing with super hot water allow you to acclimatize your body to the heat of onsen water at the start of your bathing experience.
Once you are clean, you can choose the first pool to soak in. Enter the pool carefully, holding the railing if needed to test the heat of water. I generally keep my towel folded on my head or safe on the shelf. It is considered rude to soak your towel, and long hair in onsen water, so do tie or bun up your hair before entering a pool.
Some of the recommended bathing houses in Tokyo:
Daikoku-yu 大黒湯 nearby Skytree: This public bath house is one of my favorites in Tokyo. The name literally means 'big black bath'. It is a really nice onsen especially with an outdoor area that has divine pools and a chillout area on deck where there is swings. Note that this outdoor area which every day and is on the men's side on odd days, and women on even days. One of the two outdoor pools is a large pool with milky bath that has a spacious soaking area and a sitting spot. The other outdoor pool is a refreshing cool plunge bath where you can see the top of Skytree on a clear sky. The smell of the oak/pine? pillar that is being heated from the onsen water gently wafted through the air, is so relaxing to your sense of smell and well-being. Then you can return to indoor area where there are four pools: a soaking bubble pool kept at 35 degrees thus popular for long soak and for children, a seasonal herbal pool with different water every day (when I was there on July 8th, it was rose), massage pool with super jet (at super hot 42 degrees water), and a small cooling pool. Soap and shampoo/conditioner is provided for free with no charge for hair dryer. Closed on Tuesday.
Kogane-yu 黄金湯 nearby Olinas mall, and walking distance from Kinchicho station. Its name literally means 'yellow gold bath'. This bathing house is modern looking and newly renovated. It hosted a local brewery popular with people enjoying a mug of refreshing beer after bathing. There is a large Mt. Fuji mural drawn by manga artist. When I visited it was Tuesday, and the women section has the bathing area that is relatively small with only 2 indoor pools and a small sauna with no outdoor area. From the website it seemed that every Wednesday when it switches, the women would then get the area that is hosting a more spacious sauna with exit to a relaxation outdoor area.
Sakae-yu 湯どんぶり 栄湯 nearby Asakusa area: This bath uses natural hot spring water, exclusively. It is located on a quiet neighbourhood, which is in fact only a few bus stop away from Yanaka-Ginza. The outdoor area is spacious, with bath of nano-fine bubbles (thus seemed milky) with water full of minerals. In between outdoor and indoor it has the medicinal bath that is apparently ginseng-infused water with good health benefit. The indoor area is also spacious with a cooling bath and a medium soaking pool. The pool has a unique micro-vibrator section where a small electric current would gentle shocked and vibrate your body. I lasted 3 seconds as I am scared. It supposedly stimulates and relaxes body. This bath house provides complimentary soap and shampoo/conditioner. Closed on Wednesday.
Onsen at residential neighbourhood Musashi-koyama Shimizu-yu 武蔵小山温泉 清水湯: a healing place featuring two types of mineral: gold and black water, both outdoor. The two indoor pools with black water; one has strong jets and also a resting area, and the other one a cool plunge pool. This bath house does not provide soap and shampoo although the small cashier area is selling small packets of them. There is complimentary plum-based drink in the lobby that is super refreshing.
Japanese words related to bathing:
お風呂 ofuro meaning
天然温泉 ten'nen onsen meaning 'natural hot spring'
温泉 onsen meaning hot spring
湯 yu meaning (bath) house
Post covid, I notice that there is generally even cleaner pools and hygiene practices. All water buckets also seemed to use a standard yellow plastic pail with a marking of onsen sign at the bottom.
