In my years of living in the U.K. I have never met anyone who knew their blood type, apart from just a handful of exceptions. I grew up with the concept of blood types as being an important part of who you are and what your personality is like, and many people would adjust aspects of their lives according to their blood type. The closest equivalent to this would be star signs Blood types played a big part when searching for a romantic partner, and when applying for jobs. The four blood types each have many personality traits, some of which are shared, so no two people of the same blood type will be exactly the same. Here are a few traits that are associated with the blood types:
Blood type A: Well-organised, perfectionist, stubborn, shy
Blood type B: Passionate, unpredictable, curious, outgoing
Blood type AB: Eccentric, adaptable, aloof
Blood type O: Optimistic, cautious, peaceful
I am type AB, and so are my eldest and youngest daughters. Type AB is the most rare blood type in Japan, and is often considered to be the ‘weirdo’ blood type! Since type AB is a combination of type A and B, some AB people will show more traits of one than the other. For example, my eldest daughter is far more shy than my youngest daughter which is a trait more common with type A, whereas my more outgoing youngest shows more traits of type B (I also show more B traits!)
I don’t go so far as to let blood types guide or decide anything for me, but I find discussing them and their personalities very interesting. Sometimes if I watch my children or family members interacting it’s fun to think ‘Hmm that thing he did/said is such a B type thing to do/say’ Perhaps when you’re next at the doctors ask them if they can tell you your blood type!
I recommend this article that goes into further detail on the Japanese blood personality types: https://www.tofugu.com/japan/japanese-blood-type/