I've seen them. It is a series. First one is super realistic from what I recall. Also, the first one actually caused a big stir in the states when Charlie Sheen saw it and thought it was a real snuff film. The FBI got involved.
It was marketed as a 'is it real or not' in Japan. People were concerned and the makers were forced to make a follow up showing the actress who was 'murdered'.
This was talked about at length here before.
It's mindless gore and I'm not a fan of that genre of horror in the slightest. But, you can see clips and learn more in the documentary Snuff:Does it Exist. It's free on Google video.