There's a good deal of stuff whether PG rated or not that's available in Japan that just don't make it to the US outside of released content over BitTorrent or whatnot.
Hongfire seems like a rather large community with people who do live in Japan. I'm not sure what the laws are or anything but I don't see why it would be illegal for someone in Japan to work out a deal with someone outside of it to export specific products.
Has it ever been tried before? There's some stuff i'd love to be able to purchase both out of desire for the product and desire to support the companies producing it but you know... they just don't respond to emails written to them in english so I have no idea if it was even possible to convince them to ship something out to me.
If you're living in Japan and willing to serve as some sort of medium to acquire stuff through, i'd love to work something out. Heck, I wouldn't mind if you insisted on putting the stuff up on EBay to bind me legally to make sure I paid you for the product and your services.