Water chemistry, onsen towns, rotenburo, and the unspoken rules that turn a tourist into a regular.

The difference between a nice bath and a great one is almost never the water temperature — it is the water type, the time of day, and whether you know what the room expects from you.

By the end

You will be able to read a water-quality board, pick a bath that suits your body, walk into a ryokan or a public bathhouse in any onsen town and behave like someone who has been coming for years.

Who this is for

Anyone who has already taken Part 1 or bathed in Japan once and wants the second layer: what the water is, where to go, and how not to look new.