The hotel is closed to 知床五湖, Chinese hotel name not available as it's only in Japanese. So you can tell they mainly serve locals.
知床五湖 is a great place to visit. It's one of the world's natural reserves. Breathtaking beautiful secenery with total serenity and peace. Perhaps driving is more convenient so not sure if u could do it in winter
We tried mix hotspring too but towels are not allowed, as it's traditional one. It's in the Easternmost area surrounded by natural reserves. You can see bears and dears around the hotel and along the road when driving there. We did it after midnight to make sure there's no people other than we couples. My hubby 睇水 and i hide myself in a secret corner. It's super exciting and fun!! We have been to over 10 hotsprings in Hokkaido and I'll always remember this.
It's true that there're only old women in regular hours.
I've been to Hokkaido several times and we used to travel from East to West or West to East. (不走回頭路)
What I found are places at 道東 are far less commercial and far more beautiful. You can use reasonable budget enjoying very deluxe hot-spring hotels (一泊二食) super yummy!!
When we visited 道東 several years ago, we were always the only non-Japanese staying in the hotspring hotels and you know these are real good hotels perceived by locals!! Of course, things have changed today after the movie 非誠勿擾. All deluxe hotels have staff coming from mainland China to serve the new rich.