It's also worth noting that those vending machines are only located in sex shops.
> there are also vending machines that sell used women's underwear.
While the plural is technically true, it is a little disingenuous. There are very few, probably not enough to overflow the fingers of both hands (or even, maybe one hand) in the entirety of Japan.
It's worth noting that in Japan, there are also vending machines that sell used women's underwear.