Along the 1,200k Shikoku Pilgrimage known as Ohenro there are hundreds of "rest huts". Often little more than the kind of picnic shelter you find in parks..... a roof over a table and seats..... they are where walking pilgrims can take a break from the weather, rest, eat, and quite often spend the night.
There is an organization that helps set up these huts around the island, and they are often very interesting architecturally, if not very practical from the perspective of someone looking to spend the night. There are , I think, 55 of these so far.
Some are set up just by a local community and provide free refreshments and snacks.... part of the tradition of Osettai.
The most interesting one I have found so far is this one in the mountains of Ehime. The nut itself was nothing special, but right next to it was a wood-fired bath!!!! .... I was there too early in the day to stop and try it out.....
Often these smaller locally-supported ones will have a port-a-loo next door and more weatherproofing for those needing to spend the night. This one also had a couple of electric sockets for charging phones and for other electrical appliances....... one guy I walked with for a while carried a small electric hairdryer to heat his sleeping bag while in the mountains in mid winter....