Got it...
But I don't understand the comment... "Not based off the science of it"... When, A, B, AB, O = science of it. (Didn't exist "in culture", until it was made-up by science. Has nothing to do with zodiac... Was a fictitious "belief" from a nut-job military leader in 1927's, and was based off "the science of blood". Surely to get his own family into war-jobs, or out of being used as cannon-fodder. Actually, it is the reverse of what you said. It determines your personality, your personality doesn't determine the blood-type.)
It was only a "thing" from 1927 to 1930... Unless you are talking about that other thing from the 70's from that other nut-job... The broadcaster/journalist, who was born in the 1927's era and toxified the world after his german "studies" of blood science, relating them to statistical "random" data that favored his research and funded his family.
https://en.wikipedia.org/wiki/Masahiko_Nomi
That actually, sort-of makes sense.
That is also on the same page.
Society and culture
Main article: Blood type personality theory
A popular belief in Japan is that a person's ABO blood type is predictive of their personality, character, and compatibility with others. This belief is also widespread in South Korea and Taiwan. Deriving from ideas of historical scientific racism, the theory reached Japan in a 1927 psychologist's report, and the militarist government of the time commissioned a study aimed at breeding better soldiers. The fad faded in the 1930s due to its lack of scientific basis and ultimately the discovery of DNA in the following decades which it later became clear had a vastly more complex and important role in both heredity generally and personality specifically. No evidence has been found to support the theory by scientists, but it was revived in the 1970s by Masahiko Nomi, a broadcaster with a background in law who had no scientific or medical background. Despite these facts, the myth still persists widely in Japanese and South Korean popular culture.
"The theory was imported from Nazi race ideologues and adopted by Japan's militarist government in the 1930s to breed better soldiers. The idea was scrapped years later and the craze faded."
http://www.foxnews.com/story/2009/02/02 ... ality.html
He essentially took the most common blood-type (his paying audience), and made them out to be "the best personality", by finding a "few" individuals with medical records with those specific attributes. Then wrote a book to sell, to make money, when he failed as a journalist. Simply writing about german research and applying it to the japanese. Though, in all his "tests" he was never once able to identify anyone's blood-type, based off this science that he borrowed from history. Had he been a scientist, or a doctor, or even a decent journalist, and not a fantasy-writer... I imagine he would have admitted defeat, instead of dragging his family into his fantasy. Even his son, who was damned to continue his research, has come to the realization that there is no relation. (But it still puts money in his pockets.)
https://www.human-abo.org/
The "english" "go here" page...
http://aboworld.wixsite.com/global-abo/about
Their own "contradiction"... character is not a "fixed thing"... (Essentially nullifying all their own research, within their own documentation. Something a scientist or medical doctor never does, but a journalist does. It's called back-tracking. You are good, and you are also evil, but sometimes neither, and sometimes both. Bibles do the same thing.)
http://aboworld.wixsite.com/global-abo/guid5
What he actually believes, and is fact, is stated there too...
Human being is a social animal. If the social state changed, it will give influence to each one’s action and way of thinking. Conversely, conclusion of each one’s action and way of thinking also give influence to a social trend. Society and human beings always interacts each other.
EG, blood-type has nothing to do with it. Your personality is simply "the way you choose to act, based off your influence by your peers". It is like a horoscope. Every personality can be any sign, and is every sign. That is called humanity. No individual has ever been "just a single sign". Would be a messed-up world if it was like that. (With over 90% of the world being A or O, then we are all the same personality anyways, yet, we aren't.)
But, in any event, glad you have a solution you are looking for.
Interesting read, by the way... His book. Can't wait to see your game, based off of "the science" of it.
Maybe you will find more ideas from the links above, to add to your story. I hope. There is a lot of good fiction there, to get ideas from. Even a few facts too!