It puzzels me that these Japanese people have sex in front of the geisha's as they 'marry', and even later on again and again. Like it's absolutely normal.
I can't imaging having sex with my love & order 4 prostitutes just to play us some live music and be our audience?
Why?
First, geisha are not prostitutes.
Second, in feudal times, it was normal to have ´servant´ (I´m not quite sure if they were Geisha, it´s been a while) standing beside your bed while having sex.
The film is set in 1936 so feudalism was long gone.
One can't really think of Kichizo as your average Japanese. No, Japanese peasants/commoners didn't usually hold orgies or have sex with others present and certainly it isn't something that normal people in Japan do nowadays. But a rich playboy visiting whorehouses might do.