or anyone else that knows. in my ongoing struggle to understand japanese porn I'm confronted with another question. why do they often list the blood type of the female performer? is this important for some reason? is there some type of cultural significance? thanks.

It's because the Otaku (pervert) wants to know everything about his idol (whore). So the more info he has, the more he's satisfied. They write even the weight, height, zodiac sign etc Basically as much info as possible.

Online Otaku will compare notes or trade to find out more "facts" about their idol. The more of these you have, the more of a true fan you are, and fellow otaku will admire you.

In Japan, your blood type is kind of like your zodiac sign. Theres little personality characteristics associated with each type. Its common knowledge in Japan to know your own type. When I was living there, I was asked several times by teen girls what mine was and by the look on their faces when I told them I had no idea, you would think they had just asked my name or something.

http://en.wikipedia.org/wiki/Japanese_blood_type_theory_of_personality

You might also be interested in this: back in the 90s, obsessed otaku used to research and stalk their idols to get info on what they did daily, then write online diaries about it as though they were the girl.

This somewhat became blured when the different fashions set in; kogeru, amura, b-gyaru (b-girl), ganguro, yamanba, gozosoku (biker gang girlfriends/groupies) etc

Perhaps the Japanese interest in blood type goes back to the days when they were at war at the same time with Russia, Korea, Vietnam,China, the United Kingdom, and the USA, and lotsa blood needed to be transfused.

Not really.

But ... Australia, New Zealand, India, etc., don't count?

And, they were only at war with Russia for like a week.