I'd second the Hicks book. As I recall, he used a lot of Yoshimi's work that hadn't been translated from Japanese at the time.
30-75 rapes a day ... I don't think that would be typical for the higher-end comfort women--the ones intended for the high-ranking officers. I remember from the Hicks' book that these women would be supplied with make-up and nice clothes, almost to the end. They had to look healthy and pretty for the brave Japanese warriors. The brothel would be something like a hotel in those cases. Of course, as with prostitutes just about everywhere, they're told to pretend they're happy, look grateful. These, obviously, weren't the ones brought to the front lines for lower ranks right before battle. Well, not until they got too old and worn out.
I thought of the Stockholm-like situation too: if you had a chance to be a high-ranking officer's mistress--in some long-term occupation situation--any woman would take that option over being in a brothel, even if the man was very repugnant. The man would have to get the woman before she had been "working" for long, or before she had actually been pressed into service. Don't forget how Japanese men have such a fetish about child-like bodies. (I've lived in Japan.)That would be a selling point even if a woman or girl was no longer a virgin.
Also recall, there were Japanese prostitutes all over the place, especially in China and Burma. They would cost the most. I think the pecking order went Japanese-Chinese-Korean-Filipina. Well, the lowest would be Burmese-Filipina-Indonesian/whatever is the local. But of course dark skin always would be a strike against you. I don't know where the white women would fit in there--near the top, but age would also be a factor. And I think that mostly happened in Indonesia.
There's a well-known memoir by a British-American woman that was involved in the independence war against the Dutch in Indonesia. Must have come out in the 1960's. She was in Bali from the 1930's onward, so the book also covers the Japanese occupation. Wish I could remember the title but it has (what else?) "paradise" in the title. Like "Revolution in Paradise"? Maybe because she had no sympathy for the Dutch, the Japanese let her move around freely. Yet there was a passage when a Japanese officer, the commander of a particular occupied town, was making signs that he wanted her to become his mistress.
She was able to wheedle her way out of it ... but surely there were many women that didn't have her resources. A younger woman, maybe in China, with no way to support herself, perhaps with parents and elders dead or separated from them, siblings depending on her ... that must have happened often.
What I don't believe is that this would really be love, or romance, on her part. A la the Stockholm Syndrome, depending on her maturity, she might tell herself all sorts of stories, be grateful for little favors, convince herself that he was the exception ... at least for the duration ... but how can she ever separate a Japanese *soldier* from what his army is doing to her country and countrymen?
Maybe you've recognized a similar problem in novels by old colonial white men about middle-aged colonial white men, often married, who fall in love with a kicky dusky prostitute in the sexually liberated Orient or Afrique. Or maybe it's just the "ancient" custom to hunt down a temporary local wife, who has no feelings about the matter and suffers no repercussions. Think Graham Greene. The woman--er, girl--always is a cipher, a total idiot who doesn't have a clue how the occupiers have humiliated her country, killed her kinsman, eviscerated the culture, etc. etc. (True, Asian or African men in those novels are generally too stupid to realize it as well, but ...). From a woman's perspective, these are not convincing novels.
Sorry, I got off on a tangent. You truly have set up a challenge for yourself! I want to read this novel.