Ask John: Why Is Blood Type Important in Japan?

Question:
I was just wondering if you could explain what the different blood types mean in Japan. I know that it’s part of just about every character’s profile. And I remember reading somewhere that blood type had something to do with the character’s personality.

Answer:
The Japanese fascination with blood type is said to date back to a 1916 Japanese medical report that stated that blood type was an influence on one’s personality. It’s said that the report determined that type A blood reflected a mild-mannered, intellectual personality while a B type was typical of an aggressive, rambunctious personality. Perhaps not coincidentally, type A is the most common blood type among Japanese natives. Although personality characteristics determined by blood type has no more scientific basis than personality determined by astrological sign, Japanese superstition does still place weight on blood type as a signifier of character. In an effort to give anime characters more depth of characterization, may creators will imbue characters with not only an age, hobby, birth date, measurements, weight, hair and eye color, but also a blood type. Blood type compatibility even comes up occasionally in anime. Kodomo no Omocha occasionally uses blood type to help distinguish personality, and Gainax’s Ebichu the hamster television shorts include a joke about blood type compatibility between lovers.

According to Japanese supposition:

Type A personality is calm, studious and disciplined; outwardly serious and hesitant to express emotion.

Type B personality is exuberant and cheerful, active and inclined toward dabbling in many areas, although not focusing too heavily on any single thing.

Type O personalities are peaceful and ambivalent, strong-willed, but always willing to be flexible and friendly.

Type AB personalities are delicate and considerate to others, but strict and serious with themselves.