This is a typical question asked by Japanese. One's blood group in Japan is like a bit like their zodiac sign, it (is supposed to) tell about the person's character.

I won't hide that I am skeptical about this, especially when one knows that about 50% of Japanese are "A" and 50% of Western European (and descendant in America, Oceania...) are "O", but that one can hardly say that all these people have the same, or even a similar personality.

Oddly enough, rhesus doesn't seem very important to Japanese. Most don't even know what it is. I've known since my childhood that I was O+, not O-. That's very important for blood compatibility, as O+ are universal donors, but O- have the hardest time of all blood groups to find a compatible type.

So, what's you blood group ?