This is an aging hotel trying to make up for it with amenities. You get a free pudding when you arrive, they have free (bad) coffee in the lobby, they have washing machines and dryers free of charge on the 4th floor, and they have a really nice outdoor onsen.
They also have plenty of bath robes (yuakatas) out and slippers for hotel guests to use in and out of the hotel.
That said, unlike other hotels, they gave us no information on how to act in the onsen. I use my own slippers, and imagine my surprise when leaving the onsen to find that someone had taken them. When I told the hotel staff someone had taken my slippers, they seemed not to care at all, and even said this happens often. If it happens often, why not warn people?
This hotel seems to let anyone use their onsen for a fee, so it is not just hotel guests in there. The area has many long term campers, and who knows what kind of people they are? Unlike other hotels, there is no key card entry to the onsen. If I were a women, I would only go at busy times, and with a group/friend if possible. After losing my slippers the whole place gave me a feeling on unease.
To the staff's credit they did locate and return my slippers in the morning, but the whole experience was bad. If you have anything of value, use the lockers they provide. Use the lockers even for your slippers. This hotel seemed to care very little about onsen rules, so don't worry if anyone says anything. It is better than losing your things.