Third drink. Nice izakaya. Things are going well.
"So — what's your blood type?"
You explain that you do not know, because you are from a country where this information lives in a hospital. The table reacts as though you have said you do not know your own name. Somebody says "you're definitely B". Somebody else says "no, he's A, look at how he folded his coat". The conversation continues without you for four minutes. A verdict is reached. You were not consulted.
The folk taxonomy runs roughly like this. A: careful, anxious, tidy, secretly stressed. O: generous, sociable, slightly too loud. B: creative, selfish, does whatever it wants, cannot be managed. AB: a mystery that even AB people describe as a mystery.
There is no scientific support for any of it. Large studies have gone looking and found nothing. This has not slowed it down for a second.
It shapes dating app filters, morning TV fortune segments, marketing for everything from yoghurt to condoms, and — at the ugly end — hiring conversations. There is a Japanese term, ブラハラ (bura-hara, blood-type harassment), which exists because it had to.
The origin is worse than you expect. A 1927 paper by an academic with no medical training, revived in the 1970s by a writer who sold millions of books, sitting on top of an older and genuinely nasty attempt to rank ethnic groups by blood distribution. The modern version is harmless fun sitting on a foundation nobody talks about.
Look at the distribution: Japan is roughly 38% A, 31% O, 22% B, 9% AB. Now look at the stereotypes. Type A — careful, anxious, tidy, keeps the peace — is not a personality type. It is a description of the national ideal, assigned to the largest group, with the awkward people filed under B. It is not astrology. It is a country quietly telling itself what it thinks normal looks like.
- Type B people report being told they are selfish so often that some genuinely dislike the question. There is a small publishing genre of "B型 self-defence" books.
- Ask a Japanese friend to guess your type. They will guess. They will be extremely confident. They will also be delighted, which is the actual point of the whole ritual.
- The equivalent small talk in Korea is the same question; in China it is more likely to be your zodiac animal. Japan picked blood, and committed.