Mizushoubai (water business) is the term for Japan's night life activities, such as fuuzoku (similar to prostitution but none of the illegal bits), hosting and managing (entertaining at bars), and kyabakura (night clubs).

Recently, it was decided that a high school should be founded to educate the youth in these areas where they previously had no such guidance: the School of Water Business, "Mizushou", located in Tokyo's Shinjuku ward.
The story is from the perspective of a teacher, Tanabe Keisuke, who was transferred there to help teach that school's first generation of students.