If you plan to walk from Arita station that's about 20-25 mins. It is up on a hill and you will have to walk at least 10 mins to get to a supermarket, a drugstore, and a liquor store. The host was kind enough to suggest grocery shopping right after my arrival and gave me a ride. Yet it was difficult because I had not seen the kitchen and had no idea what would be available. I ended up buying mostly pre-cooked meals.
My tatami room on the second floor did not have a key. Maybe it's safe enough.
It has a large kitchen and a living room. Wifi is provided for free but my room did not have the signal. The kitchen did not feel particularly clean but not intolerable. Again, I stayed on the second floor where everything could be done from cooking to bathing. On the first floor your experience might differ.
I did not meet the host(s) except when I arrived and left. Someone from another group staying on 2F explained to me how to use the shower, bathroom, and the kitchen area.
I did not see the factory, which I understand is a big draw for those interested in staying here. If you have a plan to come here for that perpose, the only thing I have to warn you is the location. Otherwise, you might be better off staying close to the station or considering making a day trip to Arita and staying elsewhere.