|Japanese Blood Type Personality Chart|
|Best Traits:||Earnest, creative, sensible.|
|Worst Traits:||Fastidious, overearnest.|
|Best Traits:||Wild, a doer, cheerful.|
|Worst Traits:||Selfish, irresponsible.|
|Best Traits:||Cool, controlled, rational.|
|Worst Traits:||Critical, indecisive.|
|Best Traits:||Agreeable, sociable, an optimist|
|Worst Traits:||Vain, careless.|
There is a popular belief in Japan that a person's ABO blood type or is predictive of their personality, temperament, and compatibility with others, similar to the Western world's astrology. This belief has carried over to some extent in other parts of East Asia such as South Korea.
Ultimately deriving from ideas of historical scientific racism, the popular belief originates with publications by Masahiko Nomi in the 1970s. The scientific community dismisses such beliefs as superstition or pseudoscience.
The theory first reached Japan in 1927 in Takeji Furukawa's paper "The Study of Temperament Through Blood Type" in the scholarly journal Psychological Research. He was a professor at Tokyo Women's Teacher's School. The idea quickly took off with the Japanese public despite his lack of credentials, and the militarist government of the time commissioned a study aimed at breeding the soldiers. The study used no more than ten to twenty people for the investigation. The breeding program therefore ended up with miserable results - most of the army selected by the project lost their lives. In another study, Furukawa compared the distribution of blood types among two different ethnic groups, the Formosans in Taiwan and the Ainu who live in Northeast Asia, especially Hokkaidō. His motivation for the study appears to have derived from a political incident. After the Japanese occupation of Taiwan following Japan's victory over China in 1895, the inhabitants tenaciously resisted their occupiers. Insurgencies in 1930 and in 1931 killed hundreds of Japanese settlers. The purpose of Furukawa's studies was to "penetrate the essence of the racial traits of the Taiwanese, who recently revolted and behaved so cruelly". Based on the finding that 41.2% of a Taiwanese sample had type O blood, he assumed that their rebelliousness was genetically determined. The reasoning was supported by the fact that among the Ainu, whose temperament was characterized as submissive, only 23.8% had type O. In conclusion, Furukawa suggested that the Taiwanese should intermarry more with the Japanese in order to reduce the number of individuals with type O blood.
The craze faded in the 1930s as its unscientific basis became evident. It was revived in the 1970s with a book by Masahiko Nomi, a lawyer and broadcaster with no medical background. Nomi's work was largely uncontrolled and anecdotal, and the methodology of his conclusions is unclear. Because of this he has been heavily assailed by the Japanese psychological community, although his books are phenomenally popular.
It is common among anime and manga authors to mention their character's blood types, and to give their characters corresponding blood types to match their personalities. Some video game characters also have known blood types, such as in the Street Fighter series, the Soul series, the Final Fantasy series, the Resident Evil series, and the Dead or Alive series, which lists character blood types in both the manual and in-game bios. In addition, it is common for videogame series, such as Gungriffon, Tekken, Animal Crossing, Metal Gear Solid 2 and Princess Maker to allow for blood type as an option in their creation modes. .
For a hilarious example in Korean pop culture, see Episode 9 of My Name Is Kim Sam Soon (the US English-subtitled version is called My Lovely Sam Soon). Watch Sam Soon analyze how love interest Jin Heon will deal with the dilemma of being stuck in the men's bathroom without toilet paper, based on what his blood type might be. Just how it was that Jin Heon managed to escape the uncomfortable situation remains a tantalizing mystery until Episode 13.
Laura Miller, People Types: Personality Classification in Japanese Women's Magazines, The Journal of Popular Culture, Vol. 11, No. 2, Fall 1977, pp. 436-452.