It feels like Kirishima has to work harder than most women who have sex with men for money. I say this because none of her lovers seem to want her to pleasure them. Instead, they all want to get her off. Which means Kirishima has to make a big show of excitement and orgasm every single time.
Of course, this is fiction, so we're supposed to believe that she really does get off every time. But most sex workers don't. And acting the part is a lot more work than fellatio or just lying there until its over.