Panties are a fetish for many guys, both seeing them on ladies and wearing them themselves under their clothes. Leave it to the Japanese to take it to the next level. There are sites online here in North America where you can indeed buy worn panties, it’s quite a thing among some fetishists. There’s even a market for used tampons and pads if you can believe it. There are stores and vending machines in Japan where you can buy these worn items as easily as candy bars.
There were having an issue with underage girls wanting to sell these items and a lot of the stores that do are kind of clandestine, so there likely are still underage girls selling them for cash. I can just imagine the old pervs creeping into the stores and buying girls panties with their skid marks and drippings on them and going home and masturbating with them rubbing them on their cocks and sniffing them. I’ve spoken to so many guys over the years that took panties out of hampers at homes they were visiting, panties of their girlfriends mom, mother in laws, and smell them as they get hard.
It was only common since after the second world war that Japanese ladies wore Western style panties and originally the fabrics were so pricey, only prostitutes could afford them, so the linking between panties and loose sexual morals came to be and is at the root of the Japanese panty fetish. A glimpse of panties is very arousing to ones in that culture, and panties are also prominently featured in the popular anime cartoons.