If you want to stay make sure to have a reservation. They are not always happy if people show up unannounced - especially after 1pm since they carefully prepare food in respect to the exact amount of people they are hosting.
Also be aware that the Goshikigahara
hut does not serve lunch and water needs to be purchased. However they sell some snacks and water, obviously.
Dinner is at 5pm. 🍜 Breakfast at 5am. 🍙