Oedo Onsen Monogatari in Odaiba has been described as an onsen theme park. I found that description really off-putting, so for years I avoided going. But this year I finally went with a group of friends, and I actually really enjoyed it.
First things first, it's a little more expensive than other onsen I've visited, and it feels a little less authentic. That said, I didn't think that negatively impacted my experience. This is an excellent option if you don't speak Japanese and/or it's your first time and you don't have anyone with onsen experience to go with. The staff can speak English (and I presume Chinese), and they are good at managing large groups. Tour buses often drop groups off, but it doesn't make the facility seem crowded or slow things down unnecessarily.
When you arrive, you immediately remove your shoes and leave them in a shoe locker. Then you go to the front desk and get a wristband that opens a locker and allows you to charge food, drinks, souvenirs, and various spa treatments to your tab. Next you're issued a yukata (cotton robe) and sent to the changing rooms. This is where things diverge from normal a little bit, though it's not that different from other spa-style onsen.
After changing into your yukata you enter an area that is themed like an old Edo village. It's actually very cute. There are lots of places to eat and buy souvenirs, and from here you can access the spa where you can sign up for different massages and treatments. This entire area is mixed sex, so if you're with a group you can hang out with everyone. Then when you're ready, you can head to the separate baths. In the second locker room you will be given towels, and get yet another locker (there are lots of keys to juggle) to change out of your yukata.
There are a nice variety of indoor and outdoor baths, and it's all very clean and beautiful. I will say that I've been twice now, and each time my skin smelled like chlorine after leaving. I suspect they are treating the water. This is not typical of onsen, but I suspect it is a cleanliness precaution taken because with a high volume of tourists it's possible people will make mistakes with the usual washing procedure. I did not notice any chlorine smell when I was actually in the baths, and I have a very sensitive nose, so I think it's probably quite mild. It shouldn't detract from your experience.
Afterwards you can put your yukata back on and return to the communal area if you'd like to eat, shop or rest more. If you're looking for a place to eat I highly recommend Yamagishi Taishoken. It's a branch of a very famous ramen shop that is credited with creating and popularizing tsukemen (dipping noodles).
This is a really accessible onsen, and I really appreciate that fact. But if you're looking for something that feels a little more "deep Japan" Sayanodudokoro Onsen, Utsukushinoyu, or Spa EAS might be more what you're looking for.
Oedo Onsen Monogatari
Hours: 11:00 am - 9:00 am, last entry at 7:00 am Mon-Sun
Address: 2-6-3 Aomi, Koto-ku, Tokyo
|Oedo Onsen Monogatari|
|The Edo style village|
|Lots of great photo ops|
|Yamagishi Taishoken Ramen and Tsukemen|
|The noodles are SO good!|