Japanese blood type theory of personality
http://en.wikipedia.org/wiki/Japanese_blood_type_theory_of_personality
It is popularly believed in Japan that a person's ABO blood type or ketsu eki gata is predictive of their personality, character, and compatibility with others, similar to the Western world's Astrology. This belief has carried over to certain extent in other parts of East Asia such as South Korea and Taiwan. In Japan, asking someone their blood type is considered as normal as asking their astrological sign in other countries.
