why mess with r18? Just login to dmm.co.jp digital version, use google translate and buy points on there with paypal, they accept paypal from anywhere and then buy the movie.
I have, each time you rent or buy movie you get points, after a while if you get enough points, they'll ask if you want to add points to a future purchase to lower the price.
I usually buy a movie or rent a movie thru sale, and then use the points for the monthly subscription. I can't hold on to that much porn. Plus with JAV it would take a very special movie for me to want to purchase it anyway.