Although the Japanese may have a reputation of being quite open-minded when it comes to sex, what with their open views about the need for "love hotels" in a society where the oldest sons generally live with their parents permanently, and their laissez faire attitude about mild nudity being shown on late-night broadcast TV, in truth the Japanese are extremely conservative about many things. I once went to Thailand with my wife, and we were on a beach with many female tourists from Europe who were sunbathing topless. I slyly suggested that she could do the same if she wanted, and she exploded with embarrassed reaction that would have rivaled Taiga Aisaka. The Japanese are also extremely suspicious of the European custom of friends kissing each other on the cheeks, something that gets parodied in anime from time to time ("Don't you know? In the West it's just a greeting"). Every women I've ever known in Japan uses pads instead of tampons, the idea of the latter being somehow scandalous, and if you suggest to a Japanese woman that she try using tampons she'll turn red and giggle like a little girl.
Japanese are conservative about many things.