
Although there are still a lot of things unknown about the relationships between blood types and personalities, many people in Japan (and also in Korea and Taiwan) believe that checking the blood type helps understand a person’s character. It is not uncommon to be asked “What is your blood type?” in Japan, which might be a strange question for people from western countries. The study lacks evidence but it is an interesting theory and it’s a fun topic to talk about with an Asian friend.
Let’s learn a short history about it and find out what it says about you!
How did it start?
In 1927, Takeji Furukawa (he was a professor at Tokyo Women’s Teacher’s School) published his study about blood type, “The Study of Temperament Through Blood Type” in a scholarly journal. Though he only had ten to twenty people for the investigation and the study lacked credentials, it took off with the public in Japan and many believed it.
Later in 1970s, Masahiki Nomi, who graduated from the University of Tokyo, developed blood type personality theory and published a book called “Understanding Affinity by Blood type”. His study was heavily criticized by the Japanese psychological community because Masahiko only graduated from the engineering department and didn’t have any medical background and the book didn’t include enough scientific evidence.
However, the theory itself was very interesting and the book became a bestseller. Nowadays, discussion of blood types is a popular topic especially when women talk about relationships, and it often appeares in magazines.
Blood types and personalities

Blood type A (about 40% in Japan)
Positive traits
Responsible
Perfectionist
Wise
Cautious
Negative traits
Over-earnest
Obsessive
Stubborn
The least temperate
According to the theory, people with blood type A are generally friendly and dependable, but sensitive and somewhat reserved. They prefer staying alone than being in a group. They get along well with blood type O people but have difficulties making friends with blood type B.
Blood type B (about 30% in Japan)
Positive traits
Creative
Active
Optimistic
Easy-going
Negative traits
Irresponsible
Lazy
Unreliable
Impatient
People with blood type B are active and easy-going. They are social, independent, and like to go their own ways. But on the other hand, they could be irresponsible and selfish. They get along with people with AB blood, and the worst with A.
Blood type O (about 20% in Japan)
Positive traits
Confident
Strong-willed
Competitive
Athletic
Negative traits
Arrogant
Cold
Aggressive
Envious
This blood type is the most common in the world. About 40% of people (and about 90% in Latin America!) all over the world have this type.
People with O type are energetic and confident. They are natural leaders and good at caring others. However, they are afraid of being rejected. They sometimes have difficulties expressing feelings and can be sensitive inside. They go along well with Blood type B people but the worst with AB.
Blood type AB (about 10% in Japan)
Good traits
Talented
Rational
Intelligent
Adaptable
Negative traits
Critical
Indecisive
Aloof
Not trustable
Only about 10% of people in the world have this blood type, and they have mixed characteristics of A and B. They are eccentric and talented but can be either genius or psycho. They are adaptable and can go one place to the another easily. Some people see that they are moody and not trustable because of their unpredictability.
They go well with AB and B ,but not with O.

Some claim that all this is no more than a superstition but it’s often a good topic and fun to talk about. To this day, there are many books on blood type and personality relationships in Japan.
My blood type is AB by the way. How about yours?
Did the study above show your personality?
Thank you for reading today’s post!
See you next time.
Taka
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