In typical Japanese bathroom, there is a chair and water pot.
How do we use it?
1. Sit on the chair
2. With a water pot, get some hot water from the bath tub
3. Spill hot water on your body
4. Wash your body
5. Again get some hot water from the tub and spill it your body to rinse away soap
Japanese bath tub is used for warm up your body, so it is filled with much hot water.
As the hot water in the tub is thrown away, it is wasteful so we use it even there is a shower.