Tateyama Onsen Senri no Kaze in Tateyama

I used the hot spring for a day trip.
Entry begins after 7pm on Mondays.
At the time of this posting, the weekday fee is 1,000 yen (extra if you need rental towels, etc.).
Once, when I arrived around 4pm, I was told, "It opens from 6pm," so be careful.
The hot spring has an indoor bath, an open-air bath, and a sauna.
There is no cold bath.
The open-air bath is small and can only accommodate about 4-5 people comfortably.
However, since it was a Monday, it was private, so I think it should be fine if you choose your day carefully.
The water is an unusual brown colour (like weak coffee or strong oolong tea) and has no smell.
It's dark at night and you can't enjoy the view, but it still has a sense of freedom, and the slightly warm water is pleasant.
It's not very crowded, it's comfortable, the staff are polite, the bath amenities are plentiful, and the hair dryers provided are powerful, so I think it's a pretty good facility.
However, I have two complaints.
The first is security in the changing rooms.
There are only baskets, but no lockers with locks.
I feel uneasy as day-trippers will have to store their wallets in that state.

The second issue is that there was a mysterious bonfire near the entrance.
It was night, so I don't know if it was staff who was doing it, but I can't imagine anyone other than those involved would be starting a bonfire, so I'm assuming it was staff.
The smoke reached us while we were in the open-air bath, and it was so smoky that it hurt our throats and made us uncomfortable.
It's something that should be obvious with a little thought, but I wonder why there was a bonfire in that place.
I'll deduct 3 stars for that.