I find an article "Does Your Blood Type Affect Your Personality?" which said,
There have been numerous studies that have attempted to use research and statistics to study the linkage between blood type and personality. Unfortunately, research has proven to be inadequate and restricted, as statistically inappropriate measures, methods, and samples have been utilized. This has resulted in the failure to show any statistically significant correlations between blood type and personality. Due to this fact, blood type personality theory is largely dismissed by the scientific community.
URL: https://www.e-counseling.com/mental-health/does-your-blood-type-affect-your-personality/
But this is NOT true!
One of the Japanese research (Grant-in-Aid for Scientific Research) said "We also demonstrate that significant difference on personal characteristics between blood-types by using the database on recent huge questionnaires survey", as the following:
[Investigator] Cosy Muto, Masahiro Nagashima et al.
[Title] A demonstrative and critical study on pseud-science for scientific literacy construction at teacher education course
[Abstract] We also demonstrate that significant difference on personal characteristics between blood-types by using the database on recent huge questionnaires survey.
