This curious book is an American-published pornographic novel that purports to be written by a Japanese. Though its main aim is to excite, its interest lies in the cultural assumptions it makes, these rendered suspicious by the presumptions it displays concerning the character of Japanese women.
In all pornographic writings (at least those written by men) women are usually portrayed as insatiable. They must be if the designated quota of couplings is to be achieved. This varies but the number offered by Stephen Ziplow in his "Filmmaker's Guide to Pornography" -- 10 "money shots" per film -- seems average for fiction as well as film.
In Namban's novel, however, such scenes occur every few pages. There are, indeed, so many that they get in the way of the story and I never did find out what the "yakuza perfume" consisted of. Not that anyone but a reviewer would complain. One does not read pornography for plot content or character interest.