The Japanese have a passion for filing and categorization that reaches fever pitch when it comes to the always-popular system of classifying people by their A, B, AB or O blood group — “ketsuekigata” (血液型, blood type).” Women, especially, will ask about the blood type of anyone we feel friendly toward (and will eagerly volunteer our own); the topic is regarded as a surefire ice-breaker, the veritable exchange of personality meishi (名刺, business cards), as if to say, “This is me, so what about you?”

On the other hand, after getting acquainted and telling each other about families, birth dates, etc., followed by the inevitable question of blood — “Ketsuekigata nāni?” (血液型なあに? What’s your blood type?), it could be that the other person will look a little wary or mildly disappointed. Many Japanese women know, down to the minutest detail, the characteristics of their particular blood group — and more importantly, it’s aishō (相性, suitability) with other types. A mismatch of blood types could ruin the buds of a beautiful friendship.

A widely known fact of Japanese blood is that, demographically, there are more “A gata” (A 型, A types) than any other. Key A traits are majimesa (真面目さ, seriousness or gravity) and hatarakimono (働き者, industriousness) — easily believable, judging from most people’s behavior in this country. A types are also tayorini naru (頼りになる, dependable) and shiryobukai (思慮深い, to think before speaking and weigh the consequences of actions), which makes them excellent advisers and genuine friends.

Other well-known A characteristics are an obsession with cleanliness and a deep-rooted fear of contamination. The reason behind this (only hearsay, but I’m told there’s truth behind popular myth) is that when the country opened its doors to the outside world in the late 19th century, a host of exotic diseases came in (cholera was the biggie), and only those who had notions of hygiene and cleanliness were able to survive the storm. They were, coincidentally, A-type people. The other types, less concerned with security, hygiene and common sense than their fellow A’s, became sick and died off in droves. The A’s, however, lived to breed and extoll the virtues of cleanliness.

Mori Ogai, a celebrated Meiji Period (1868-1912) novelist and reputedly a raging A, was famed for his staunch refusal to share bath water, even with his own family. He washed himself from four buckets filled with hot water, lined in a straight row in the hallway of his house. He also advised the government to demolish all sentō (銭湯, public bathhouses) in the interests of kokumin no kenkō (国民の健康, national health).

From the A-type point of view, B-type folks such as myself comes off as slobs. The other day, I was caught wiping my hands on my jeans as I came out of the restroom (Is that a crime? Is it? Huh?) and a colleague gave me a long, accusatory look before saying (and his words came out like bullets): “Wakatta. B gata deshō?” (わかった。B 型でしょう? I get it. You’re B type, aren’t you?) I don’t think he and I will be having lunch anytime soon.

Indeed, B types are often seen as the black sheep of the Japanese race, inviting verdicts such as wagamama (わがまま, selfish), maipēsu (マイペース, my pace, or doing things at one’s own pace), and kawatteru (変わってる, strange).

Not surprisingly, statistics show that a marriage between an A type and B type is most likely to end in divorce; particularly disastrous is when the woman is B and the man is A. Type O’s, on the other hand, are acknowledged as generous, passionate lovers with hearts of gold and wallets to match. Type O’s have a talent for financial success, thrive on parties and social engagements and generally sport a Latin temperament rarely glimpsed in the sober Japanese.

The rarest (and therefore most appreciated) blood type in this country is AB. An AB person is well balanced (coming from a masterful combination of the best A and B qualities), clearsighted and logical, with the ability to remain cool in the face of utter pandemonium. It’s said that many AB’s choose careers in the police force, bureaucracy and scientific academia — they are the shussegashira (出世頭, high-flyers) of Japanese society and beacons of light in times of severe stress.

Interestingly, few Japanese will try to apply these blood-type rules to foreigners. This is probably because of the one trait that applies to all four blood types — meiwaku wo sakeru (迷惑を避ける, an unwillingness to impose).

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