Niwanoyu

We stumbled upon Niwanoyu because we wanted to find a co-​ed onsen so we could experience it together. Also, like Hana S., we wanted something relatively close to Tokyo because our trip was so short.
One thing we noted was that the staff spoke little English, however, the signage was decent. It required some investigative work, but I had no issues understanding what I had to do, except I went in my bathing suit for the female only portion and was gestured (quite politely!) that bathing suits were not allowed in the area.
Before you come in, you should take off your shoes and place them in the lockers to the right. After, go and pay for the entrance fee immediately on the left. They will give you a locker key (that you wear on your wrist) and a small bag with the onsen pajamas. We left our valuables (money and passport) at the lock boxes right next to the reception area at no charge. It took a little navigating as there were no signs in English, however, we eventually figured it out.
There are quite a few areas in the onsen. The main indoor pool featured jets used for massages. I couldn’t be pulled away from this area. It was just SO relaxing. There was a small wait on some of them as there were a few that hogged the jets. However, because we went earlier in the day, it wasn’t an issue. There were also two saunas in the indoor area. I was a fan of the mineral sauna. There is a bucket shower right outside that one that was fun to do.
There was an outside area with hot tubs. One had an amber color likely due to the inserted mineral, while the other seemed to be just hot water. There was also another sauna in that area. The outside had a beautiful garden that you could stroll through. If you wanted to relax outside, benches were scattered throughout. There was a small waterfall for viewing purposes only.
The gender-​only sections were nice and less occupied than outside. I sat for a long time in the mineral full body jet section as no one was there. It was heavenly!
Upstairs there is a small gift shop that seemed reasonably priced (we used Amazon to do a price comparison). The armchair area was super quiet, so we didn’t partake as we wanted to chat.

We loved our experience at this onsen. It felt very authentic without being too far from the center of Tokyo. No one here spoke much English but it was easy enough to get around. Just make it a point to read the signs and you’ll be able to navigate without any faux pas.
Immediately upon entering, remove your shoes and put them in a locker. You’ll give the key to the front desk when you check in. You can pay with cash or credit card. They will give you a set of clothes that are like pajamas to walk around in. They will give you a wristband that has your key and locker number. All of the extras within the facility are tracked to your locker number and you will pay the balance when you leave. Don’t worry about carrying around cash or card within the place because you will only pay when you return your locker key and get the key back for your shoe locker.
The shared area in the pool and outdoor hot tubs were really nice. Hubby and I met in the pool and enjoyed the different water jet massages. The outdoor hot tubs have a really nice view of the garden and a small waterfall. There is also a mixed gender sauna outside that you can relax in.
Upstairs has a room with recliners and big towels where you can relax and take a nap. This room was extra relaxing! There are also options for a full body massage, reflexology, and face massages. There is a restaurant with Japanese style or western style seating.
We really enjoyed our afternoon at the onsen and I highly recommend to try it out!

Take Oedo line to Toshimaen, exit at A2. As you exit the station, take a left and then your first left. Walk straight down till you see family mart straight ahead and Starbucks to your right. When you reach family mart, take a right and walk down a few minutes. It will be on your left after the amusement park.
Great facilities! Common area for both men and women (bathing suit required), has a giant pool with jets, two outdoor jacuzzis, a sauna and steam room. There are also separate female and male onsen baths (must be nude).
Upstairs has resting area (dark/​aromatherapy room), a room with tvs, massage area (extra charges), and dining.
Fun place to relax and rejuvenate!

We were looking for two main things in an onsen: 1) pools where my bf and I could meet to hang out 2) a place that was affordable and still near Tokyo (aka not an obscure onsen that requires a taxi after a metro trip). After doing a lot of research and consulting Unilocal,this place seemed like a good pick. In fact, we liked it so much that we came back twice in a one week period!
Price: If you come after 6pm, they have a great night discount of 1,295 yen per person (but 2,310 yen regular price). We took advantage of this discount both times.
Check-​in process: Umbrella locks are available outside, and there are shoe lockers for a 100 yen deposit (you get it back at the end of your stay). Then, at the front desk, you pay, turn in your shoe key, and receive your goodie bag with a large towel, small towel, and onsen pajamas (similar to jimbaes with pants). Most importantly, you will receive a wristband with your locker key and a barcode, which you can scan to make purchases inside. This locker key is wearable in the pools and allows you to leave your wallet in the main locker for safekeeping. There are mini security lockers in the lobby for valuables and bigger lockers inside for your clothes, backpack, etc. Now, you are free to either a) change into your provided loungewear and hang out on the second floor b) shower and change into your swimsuit to go into the mixed gender pools or c) shower and go into the single gender baths. Choose your own adventure!
Mixed Pools: The mixed gender pool in the middle is lukewarm and has strong jets where you can get a massage. There is a small hot bath inside and 2 other hot baths outside. Additionally, there is a wet sauna inside and a hot sauna outside available. My favorite were the outside pools because you could gaze at the stars and cool off even with the ~ 40 degree Celsius water.
Single Gender Pools: For the females, there was a clear hot water bath inside and outside, 1 reddish brown bath inside, 1 cold water pool, and 2 cute single person baths outside (one reddish brown and one black). The single person baths looked like big flower pots, and were my favorite! One of the baths inside also has full body jets where you can lay down and get a shoulder to feet massage. Very cool.
There are both sit down showers and standing showers, if you have a preference, and body soap, shampoo, and conditioner are all provided. Afterward, there are vanity counters with hair dryers, Q-​tips, combs, hair water, and face water for your use.
2^nd floor: Upstairs there is a nap room, sitting room with individual TVs, café, souvenir shop, massage areas, and a restaurant. The restaurant closes roughly around 9:45pm, so I suggest heading over early if you want to have a meal. The nap room was wonderful, with large recliners and big towels available. Each recliner has different radio stations where you can choose your personal music (ocean waves, classical, etc.) Some of the recliners don’t have a divider between them for couples, and there is a ladies only section on the far right.
We ate at the restaurant once, which was a little pricy (around 600 yen for an appetizer), but good. As a treat, I got a 20 minute back/​shoulders massage, and it was fantastic! If you speak to the massage desk downstairs, they will hand you an English pamphlet and assist in making a reservation. I talked to them at 6:00, and I got a reservation for 6:10 — 6:30, which was perfect. It cost about 2,100 yen for the session, and I loved it!
Check-​out process: The onsen closes at 11pm, and if you leave at that time, there will be a neat and orderly line showing exactly what to do. In sum, you line up at the front desk to return your goodie bag and pay off any charges made to you wrist band (food, massages, etc.) Then you collect your shoe key, and you are good to go!

I found this place on Unilocal and hoped on the train over the next night for a nice relaxing soak. It is cheaper than the onsen in Odaiba and a bathing suit is only 400 yen for rent so I rented one to try out the co-​ed areas, but you can bring your own suit or buy the suits that they have in the lobby for like 8000 yen minimum. Overall, the same-​sex areas are really nice on their own. No need to bring soap or shampoo. They provide towels and pajamas for you. I don’t know a lot of Japanese and I was by myself, but I managed on my own.
You have to rent your own shoe locker, then give them the key at the counter for a key to a locker. They give you a bag of clothes and 2 towels. I took my stuff and my rented suit (which is way conservative, by the way) and went on my way. Shower first then try out the baths. They have so many different baths it is easy to relax and never be bored! I love the eucalyptus steam room! They have sinks inside to cool off without having to leave. They have indoor and outdoors baths. It is so relaxing!
The coed area includes a large hydrotherapy pool that is indoors. People walked around in the pool or stood by the roaring jets and waterfall like fountains. If you walk outside, there are 2 baths outdoors and a small hut with vending machines. You can slip on the slippers and take a walk around the garden which is really pretty and full of the beautiful nature that is in Japan. They have a large koi pond as well. It is so relaxing!
After you are done bathing, you can dress in your pajamas (technically, you can do this before bathing), and then go upstairs to eat at the restaurant, sit in the massage chairs, or rest in the cush lounge chairs. It is really relaxing, but as a tourist with little time, I did not feel the urge to sit around.
I really loved this onsen compared to the one in Odaiba. It is closer to get to, but really, once you leave the onsen, there is nothing in the area to visit aside from the Buddhist temple neighborhood that I happened upon when I walked in the wrong direction. I tried to find a cheaper restaurant to go to but there were very few actually open. More were closed than open. There aren’t even many convenient stores in the area either. Anyway, I highly recommend this great onsen!

A true Japanese experience!
This was my first ever public onsen, and luckily we had 2 friends who spoke Japanese to accompany my husband and I so they were able to tell us what to do, which was good because there were no signs in English. There are sections for women only and men only, but I was told that this is one of the few onsens in Tokyo that have co-​ed spaces.
Now this might scare some people, but as this is a public onsen, you will have to be completely naked when you go into the heated pools in the same-​sex areas. (Obviously, you wear a bathing suit if you are in the co-​ed areas. You can bring your own or rent one.) Walking in to the locker rooms, there were naked women, and all the showers were just open stalls with no curtains or covers, so yeah, unless you’re using the toilet, there’s really nowhere to hide.
After undressing, I was told I needed to shower. All the showers had the amenities — shampoo, conditioner, face wash, and body wash. Once you’ve showered, you can go into the heated pools. Some had special minerals/​chemicals to make your skin better, while others were simply heated hot tubs. What was awesome was they had heated pools outside, so although it was freezing walking outside butt nekkid, once you got in the pools it felt so nice!
Afterwards, they had a room with hair dryers, and they even provided q-​tips, brushes, and face lotion. You can also go to the café in the pajama-​like clothes they give you and get tea, beer, and other snacks. I loved how everything was cashless; the locker key that they give you has a barcode that can be scanned when you get any drinks, and after you’re done they scan it and you pay your extra charges.
This was definitely a highlight of my trip, as I’ve never done anything like it! If you’re interested, do bring a friend (who can preferably speak Japanese… and that you’d be comfortable with if they saw you naked.)