You enter in the middle, in what in Japan would be called the Datsuiba, or changing room. Bruce Smith and Yoshiko Yamomoto describe it as
a comfortable space for taking off one’s clothes and for drying off and putting on fresh clothes after the bath. it is a transition space between the watery world of the bath and the dry world of the house.
To the right I have drawn a room for the toilet. To the left is the bath, with the shower separate from the tub. In my post Save Water; Shower Japanese Style I described the process of showering before bathing:
To clean yourself before you got into the bath water, you did not use a conventional shower, but sit on a stool with a wooden bucket and ladle, soap and a sponge, and in the more modern showers, a hand shower that was is used when needed for rinsing and never left on to run into the drain. Sitting while you shower is safer and I found a lot more relaxing; having no water running meant that I could take as long as I wanted.