[Beware of oxygen deficiency] A secret hot spring in Nagayu Onsen?

"Suijin no Mori" is located in Nagayu Onsen, Taketa City, Oita Prefecture. Nagayu Onsen is famous for its carbonated springs, but this one was especially amazing! Carbonated springs = carbon dioxide, so when you enter a hot spring full of carbon dioxide, your brain determines that your body is lacking oxygen and commands your body to carry oxygen, which improves circulation and warms you from the inside. The carbon dioxide that was blown out and accumulated near the hot spring outlet made it really hard to breathe. I had to stand up every now and then to breathe in fresh air. I was surprised at how concentrated the hot spring ingredients were, so much so that they crystallized! It's definitely worth going at least once. *The spot is a dam, but it's a hot spring lodge that you can stop by to enjoy.