I like Japanese hot springs. So, I recommend Japanese hot springs to foreigners.
I think the hot spring village close to Shinjuku, named Isawa Onsen, is good.
It can be reached in one and a half hours.
When staying at a hot spring inn, it is better to stay at a Japanese style inn (Nihon Ryokan) rather than a hotel.
There we can sleep in futons (Japanese traditional bed) on tatami mats.
They offer traditional Japanese foods and Yukata, Hanten, Dotera (traditional Japanese Kimono).
The Roten-buro (Open-air baths) are particularly good, bathing under the blue sky in winter while watching the snow, young leaves in spring, the sun in summer, and the autumn colors in the fall. Bathing in autumn is my favorite.
I recommend a Japanese hot springs to foreigners, where the mind and body are healed.
Winter season
Spring season
Summer season
Autumn season
Photos by Internet.
That's it.