If you use Google translate for Pornography into Japanese it comes back with some weird symbols. I checked to see if those-symbols.com was available and it was. I then checked the search volume and there was 45k exact searches for the phrase. Although this wasn't in the millions I suspected it's enough to easily turn a profit on the domain if you can get ranked. However, it was very low for 'Pornography' and I was surprised it was available. After doing some research I found out I had actually bought the Japanese for 'child-porn'.com... DOH! Ruddy Google translate!
Porn in Japanese would be "ãƒãƒ«ãƒŽ" which has been taken ages ago & would be worth heaps of $$$$$ The motto is don't trust Google Translate or any other translation software, you have to check it very well. I presume you got "å…ç«¥ãƒãƒ«ãƒŽ" as the translation?