Reading Japan - The Out-to-Sea Bathhouse

The protagonist is tired from traveling and randomly stops at a small-town public bath. The ticket machine has rather odd names that might refer to private bathing rooms. Puzzled, he pushes one of the buttons and goes inside, only to encounter a bizarre scene, unlike anything he's ever seen. He pretends that he's not a first-timer and ventures into the bath without getting any explanation. He has embarked on a big adventure.