Borawazawa Hot Spring

Dorinozawa Onsen — the cheapest onsen in Tokyo, 0 yen. One bath inside, temperature 39, clear with no smell, water composition shown in the picture. Concrete bath, spacious and deep, sitting in it the water comes up to your chin. A pipe feeds fresh water with bubbles into it. No soap, there are lockers, hot water, and a standard shower. Drink vending machine but no milk. Top-tier experience, especially the location in a very quiet fishing port.