Some people in Japan believe your ABO blood type governs your personality. The concept was born in the early 20th century and popularised in the 1970s by a book by journalist Masahiko Nomi. He called the idea “blood type humanics”.

This pseudo science has crept into many facets of Japanese modern mytho-lore and is a sure fire ice breaker during speed dating, for deciding on types of diets and it turns out for finding out what character traits video game characters have too!