I had an absolutely amazing time at Nasubi.
The hostel is about a 12 min walk from Fuji station and quite easy to get to. I stayed in a mixed dorm for 3 nights. The beds was SUPER comfortable and cozy, had plenty of privacy, and were very clean. There was also sufficient space for everyone's bags in one corner. The rest of the common areas (fully usable kitchen, bathrooms, toilets, lounging area) were very clean and cozy but spacious. There are a lot of card games, books, drawing pads, video games in the common spaces. Also the atmosphere in the hostel was so peaceful and quiet but everyone was also very friendly. There are convenience stores and supermarkets. Also museums, gardens, Mt. Fuji viewing points around (I walked but you can borrow the bikes they have).
Finally, the owner, Kazu and the rest of the staff (I only got Mako's name, who checked me in, but there was another sweet staff member whose name I forgot to ask) are warm, welcoming, helpful, and so kind.
I would 100% recommend this to anybody!