The idea originated in Japan in the late 1920s, and later spread throughout Asia.
A friend of mine was was talking about guys. I guess she met a new guy, but then she found out that his blood type is AB. Her ex-boyfriend was type AB, so she won't date the new guy.
There is even a movie here, a romantic comedy, that has to do with blood type: My Boyfriend Is Type B (B형 남자친구).
Look around on the net and you will find tons of things to do with blood types and personalities.
Check out "Hey, baby, what’s your blood type?"
I'm type O. Want to know what that means???
Type O Blood people are said to set the mood for a group and to take on the role of creating harmony among its members. Their image is one of taking it easy, of being peaceful and carefree. They are also thought to be big-hearted and benevolent, and they tend to spend money on others generously. O Types are generally "loved by all." But, they also, surprisingly, have a stubborn and strong-willed side, as well, and tend to secretly have their own opinions on things. On the other hand, they have the
flexible, adaptable side of readily accepting new things. They are easily influenced by other people or by what they see on TV. They seem to appear level-headed and trustworthy, but they often slip and make big blunders inadvertently. But that is also the point that makes O Types lovable.