In Japan, asking someone's blood type is as common as asking their zodiac sign in America. But it's not just casual conversation—companies have asked for blood types in job interviews, dating apps match couples by blood compatibility, and people blame bad behavior on being "type B." This pseudoscientific belief has zero evidence behind it, yet it shapes hiring decisions, relationships, and daily life for millions.
The practice is called "ketsueki-gata," and surveys show that 99% of Japanese people know their blood type. According to the theory, type A people are organized but anxious, type B are creative but selfish, type O are confident but stubborn, and type AB are mysterious and logical. These personality profiles are treated with the same seriousness Americans give Myers-Briggs tests—except with actual consequences.
The belief started in 1927 when psychologist Takeji Furukawa published "The Study of Temperament Through Blood Type." His research used laughably small sample sizes and no statistical controls, but it caught on anyway. The Japanese military even used blood type to organize soldiers during WWII, convinced that certain blood types made better fighters.
The practice faded after the war but roared back in the 1970s when journalist Masahiko Nomi published bestselling books on blood type personalities. One book sold over 5 million copies. TV shows started featuring daily blood type horoscopes. Magazines published compatibility charts. The pseudoscience became so embedded in culture that questioning it seemed strange.
The discrimination is real and has a name: "bura-hara" (blood type harassment). People with type B blood are stereotyped as selfish and difficult, affecting their job prospects and relationships. Some companies have been caught grouping employees by blood type or assigning work based on perceived blood type traits. Schools have reportedly separated students by blood type.
Dating culture is particularly affected. Women's magazines publish romantic compatibility guides based on blood type. Dating agencies cater to blood type preferences. People have ended relationships after discovering their partner's "incompatible" blood type. It's astrology, but treated like a legitimate personality assessment.
The scientific community has thoroughly debunked this. Multiple studies show blood type explains less than 0.3% of personality variation—statistically meaningless. Any perceived correlation is likely due to self-fulfilling prophecy: people learn their blood type's stereotype and unconsciously adopt those traits.
Yet the belief persists. Morning TV shows feature blood type segments. Celebrities' blood types are listed on their Wikipedia pages. Product marketing sometimes targets specific blood types—blood type-themed bath salts, drinks, and even condoms have been sold in Japan.
The phenomenon isn't unique to Japan. South Korea and Taiwan have adopted similar beliefs, though not as intensely. But Japan remains the epicenter, where something as arbitrary as blood type can influence your career trajectory and love life.
Here's the irony: blood type actually does affect some health risks. Research suggests certain blood types have slightly different susceptibilities to specific diseases. But personality? There's absolutely no biological mechanism that could link blood antigens to behavior, mood, or temperament.
The Japanese government has tried to combat blood type discrimination. Official warnings tell employers not to ask about blood type in interviews, but many still do. The practice is so normalized that many people don't even recognize it as discrimination.
Blood type personality theory persists because it's culturally embedded, not because it's true. It provides easy explanations for complex human behavior, gives people something to bond over, and offers a sense of identity. The same reasons astrology thrives in Western culture.
The difference? In Japan, this pseudoscience has real consequences for employment, education, and relationships. It's not just harmless fun when your blood type determines whether you get hired.