[Access] 2-minute walk from Tsurumaki-Onsen Station on the Odakyu Line
[Price] 1,000 yen (2-hour limit on Saturdays and Sundays)

Tsurumaki Onsen is only about an hour from Shinjuku via the Odakyu Line, making it one of those wonderful spots where you can suddenly think “I want to go to a hot spring!” in the afternoon and actually make it happen. The water is a slightly alkaline calcium-sodium chloride spring, famous for having an exceptionally high calcium content. You can see several medical rehab facilities in the area, so the healing benefits must be the real deal.
There’s a relatively large indoor bath and an outdoor bath where, although there isn’t much of a view, the fresh air feels amazing. The indoor bath is kept at a slightly lukewarm temperature, so you can really take your time and soak. It’s a bit of a bummer that there’s a slight hint of chlorine, but the water feels soft on the skin and does a great job of warming you to the core.
On weekends, there’s a 2-hour time limit for 1,000 yen, but that’s usually plenty of time unless you’re planning on getting a massage. I typically spend 40–50 minutes relaxing in the tub and then just lounge around in the rest area. Then again, they have a stylish little soba shop that serves handmade noodles and Oyama tofu, which looks pretty good—so if you’re eating, 2 hours might actually feel a bit short! (lol).
Also, the facility is kept incredibly clean, which makes for a really pleasant visit; you can tell they put a lot of effort into maintenance. In that sense, it’s totally worth the price. I think I’d be in heaven if I could just come here on a weekday and spend the whole day doing absolutely nothing.