Insurgencies in 1930 and in 1931 resulted in the deaths of hundreds of Japanese settlers.
The purpose of Furukawa's studies was to "penetrate the essence of the racial traits of the Taiwanese, who recently revolted and behaved so cruelly." Based on a finding that 41.2% of Taiwanese samples had type O blood, Furukawa assumed that the Taiwanese rebelliousness was genetic.
On the other hand, there are opinions that the statistically meaningful differences according to the blood types are not explained only by beliefs, nor are they a self-fulfilling prophecy.
In conclusion, Furukawa suggested that the Japanese should increase intermarriage with the Taiwanese to reduce the number of Taiwanese with type O blood. It was revived in the 1970s with a book by Masahiko Nomi, a journalist with no medical background (he graduated from the engineering department of University of Tokyo).This is similar to how astrological signs are perceived as influencing factors in a person's life in other countries.One of the reasons Japan developed the blood type personality indicator theory was in reaction against ethnic stereotypes coming from Europe.In the 1990s, difference due to blood types was stabilized and variances became smaller.Then in the 2000s, difference was definitely statistically significant, too.