Personality traits associated with various blood types, according to Japanese superstition:
Type A:
Best traits: Conservative, reserved, patient, punctual, perfectionist, and good with plants.
Worst traits: Introverted, obsessive, stubborn, and self-conscious. Anal retentive.
Famous examples: George H.W. Bush, O.J. Simpson, Britney Spears
Type B:
Best traits: Creative and passionate. Animal-loving. Optimistic and flexible.
Worst traits: Forgetful, irresponsible, individualistic.
Famous examples: Akira Kurosawa, Jack Nicholson, Luciano Pavarotti
Type AB:
Best traits: Cool, controlled, rational. Sociable and popular. Empathic.
Worst traits: Aloof, critical, indecisive, and unforgiving.
Famous examples: John F. Kennedy, Marilyn Monroe, Mick Jagger
Type O:
Best traits: Ambitious, athletic, robust, and self-confident. Natural leaders.
Worst traits: Arrogant, vain, and insensitive. Ruthless.
Famous examples: Ronald Reagan, Queen Elizabeth, John Lennon
Interestingly, Type A blood is the most common in Japan, while Type O is most common in the United States — and among Japanese prime ministers.
https://www.tofugu.com/japan/japanese-blood-type/