Much as how astrology is seen in the Western world, some Japanese are very conscious of a person’s blood type, or ketsuekigata 血液型. Personality, behavior and most importantly compatibility (aka aishou 相性) with another person of a different blood type are topics that have become integrated with daily life but should be taken with a pinch of salt. Books, diet, and even condoms have been customized to each blood type. Television channels have daily forecasts for each type much like the horoscope in the papers. Characters in anime, manga or games are also typecast according to blood type.
However, some Japanese take it very seriously and pass judgment on friends and partners just by their blood type. It’s a self-fulfilling prophecy if you ask me; if you believe something of someone, it will happen, if only to your eyes.
The proportion in Japan of the 4 blood types are 40% for A, 30% for O, 20% for B and 10% for AB. The study of the correlation between blood types and personalities was pioneered in the early 1900s, and was shortly after adopted by the Japanese military even though it remained scientifically unproven. I am a blood type B and I do identify with some of the stated traits of a B but definitely not all! Blood type A is more commonly found in the Americas and Europe, and type B in Asia. Given with that probability, I would unfortunately have to refute the theory of personalities personally, as people I’ve met do not seem to have an apparent trend between their characters and their country of origin!
As the fad became more widespread and common, it became customary for the Japanese to declare their blood type on dating sites and other online forums. Job application forms also may include a blood type field so as to “better assess the candidate’s fit” to the company. In general, the minority B and AB groups are seen to be the black sheep who stand out from the norm in the homogenous Japanese society. The act of discrimination by blood type is termed burahara. Who knew that genetics had so much clout in society!
In a nutshell, be it superstition, sweeping generalizations or popular belief, it is interesting to note the extent of people’s beliefs as well as the impact it has on their outlook on life and human nature.