Tiny Use Case 5 Part I – Blood Type and Character Personality

Within Japanese visual media works, it is not unusual to find mentions of a character’s blood type within the work proper or within connected texts such as databooks, author interviews etc. In Japan blood type is widely believed to be a predictor of personality and temperament, each blood type corresponding to a set of temperaments, personality traits and quirks. The listing of a character’s blood can be found across multiple media types and franchises, with popular intellectual properties such as NarutoOne PieceBleachAttack on Titan and My Hero Academia all featuring information regarding a character’s blood type in one way or another. Do these beliefs about the connection between blood type and personality translate into character designs? Do these representations reflect popular beliefs circulating in Japan or do they differ? We took these questions to our data sources in our fifth tiny use case.

Tiny use case five employs data from The Visual Novel Database (VNDB) and data from the Anime Character’s Database (ACDB). VNDB and ACDB are different in their thematic focus and descriptive data model. VNDB focuses exclusively on visual novel games, while ACDB, although it labels itself as an anime characters database, takes a more holistic approach, including characters from anime, manga, visual novel games, video games etc. Their descriptive model is also significantly different: VNDB employs a granular model for describing characters, with traits describing characters from both a visual and a narratological perspective, character blood type being one of the data points. ACDB, on the other hand, employs a different system: characters are indexed according to six visual traits (eye color, hair color, hair length, age, gender, and presence of animal ears). A separate field of extra details such as character blood types or the fact that a character is wearing a uniform, headphones, has a beard, the color of their skin, and so on, along with a system for free-form tagging. Both sources register blood types, albeit in a different fashion: VNDB records blood type as a character trait chosen from a set list of options; ACDB lists character blood type as part of its ‘Extra-Detail’ system, with Blood Type as a label for free-form content.

While it is not uncommon to have a character’s blood type listed as part of a character’s attributes, blood type does not usually play a direct part in narratives or their wider fictional worlds. Rather, it appears to be a way to describe a character in a pseudo-holistic fashion, drawing upon beliefs regarding blood type and temperament. Such beliefs coalesce around the so called ‘blood type personality theory (血液型性格論 ketsuekigata seikakuron)’, whose emergence can be dated back to 1927, with the publication of a paper by Furukawa Takeji, a professor at Tokyo Women’s Teacher’s School. The idea gained some traction within the Japanese public, but its real popularization is more recent, traceable to the work of journalist Nomi Masahiko in the 1970s. Nomi re-purposed the theory in his later book Ketsuekigatade Wakaru Aisho (Understanding Affinity Through Blood Types), which employed blood type as a way of gauging one’s compatibility with prospective romantic partners.

Success of the book led to Nomi and his son establishing two organizations devoted to the research and development of ‘blood type personality theory’: the ‘Institute for Blood Type Humanics’ and the ‘Human Science ABO Center’. A number of papers authored by persons affiliated with these two institutes are in circulation, questionable scientific validity of the ‘blood type personality theory’ notwithstanding. At the same time, there are a number of papers attempting to explore correlation between blood type and personality traits from the perspective of psychological sciences. Various permutations of the theory offer similarly vague descriptions of the personality traits associated with each blood type, making the reader vulnerable to the Barnum-Forer Effect, eliciting interpretation that matches the reader’s expectations.

In order to be able to compare the claims of blood type personality theory to the character information in our databases we need to establish a set of traits corresponding to each blood type as posited by the theory. The closest example we have to a ‘canonical’ set of descriptions can be found within papers by authors affiliated with one of the institutes founded by Nomi. One such recent paper, by Kanazawa Masayuki, provides the following descriptions:

Blood Type Personalities Descriptions (Kanazawa 2021, 7)

Blood TypePersonality
A “Cautious about new actions, also pursue stability, but sometimes obsessed and burst into a rage. Desire for molting. Always try to improve. Take a brave action in an emergency. Go step by step after convinced. Formula-like. Prudent judgement, although draw the clear line. Strongly suppressive outside vs violent inside. Recover slowly after got hurt. Concentrate on one at a time.”
B “Look for a life with much freedom. Particularly dislike rules or formulas. Do not hesitate to take new actions. Tend to be absorbed in strongly interested things. Multitasking and go overboard. Quick and flexible judgements. Pragmatic and do not draw the line. Emphasize scientific accuracy and validity. Feelings sway, moody. Frankly express anger or sorrow. “
AB“Good reflexes, business-like efficiency. Quick and easy understanding. Rationality itself. Good critic and analyst, multi-angle interpretation. Duality with a calm, cool stable side and an easily disturbed side with sentimental fragility. Able to do everything accurately. Good at designing but not cleaning up. Smiling and soft, but keep a certain distance from others.”
O“Purpose oriented. Head straight for a target. Great achievement power. However, do not endure meaninglessness. Give up early if no good. Weigh losses against gains correctly. Hold a belief. Articulate and logical, but somewhat straight. Simple minded in part. Emotions are usually stable and do not linger. Deeply moved. Lose heart when cornered.”

The descriptions provided by Kanazawa, who is affiliated with the Human Sciences ABO Center, a Nomi organization, are not particularly conducive to the kind of research we can perform on our data. The description are excessively vague, and cannot be connected to our data points without eliciting an excessive amount of interpretation on the part of the user. At the same time, Kanazawa makes use of research results from three different surveys conducted by several Japanese psychologists. The first, performed by Yamazaki and Sakamoto (1991), examines 177 university students in regard to 24 personality traits, as part of an annual opinion poll commissioned by the JNN Data Bank, a department of Tokyo Broadcasting Corporation [a major Japanese TV Network]. This first survey is connected to self-statements such as “I have a lot of friends” (Kanazawa 2021), making it also unworkable. The two other surveys provided by Kanazawa, the former a free-answer survey on 197 university students performed by Sato, Miyazaki and Watanabe (1991) and the latter a survey on 102 university students involving applicability of personality traits abstracted from multiple books, performed by Watanabe, result in more workable statements, and are listed as follows:

Blood Type Personalities Descriptions ( Sato, Miyazaki and Watanabe, 1991 and Watanabe 1994, cit. in Kanazawa 2021, 7)

Blood Type Personality
A “Meticulous, Nervous, Serious” (Sato, Miyazaki and Watanabe, 1991).
“Considerate, careful about everything, Polite, Esteem principle than practice, Responsible, Introvert” (Watanabe 1994).
B“Self-paced, Individual, Lukewarm, Egoistic, Self-centered, Optimistic, Pleasant” (Sato, Miyazaki and Watanabe, 1991).
“Lack of prudence, Self-paced, less influenced by the surroundings, Active and curious; Optimistic” (Watanabe 1994).
AB“Dual personality, Two-faced, Oddball, Hard to understand” (Sato, Miyazaki and Watanabe, 1991).
“Moody and sometimes seen as dual personality, Cool and businesslike, Avoid close human relations” (Watanabe 1994).
O“Big-hearted, Laid back, Unassuming” (Sato, Miyazaki and Watanabe, 1991).
“Pleasant, Positive, person of action, Passionate, Show the utmost courage and guts for the target” (Watanabe 1994).

In the context of our tiny use case and available datasets, Saki, Miyazaki and Watanabe’s (1991) descriptions are the most usable – even though they might not be fully substantiated – as they are composed of one-word personality descriptors, which do not elicit excessive interpretation on the part of the reader.

The VNDB and ACDB datasets provide different and interesting perspectives on the above. VNDB offers us the possibility of an in-depth analysis of the usage of blood types, as it contains traits for each blood type, and the articulate system of personality traits we have employed in past TUCs. VNDB is also focused on a niche media format (visual novel games), whose focus on interpersonal intimacy might elicit a distinct view on the importance of listing character blood type in the eyes of the VNDB community.  Such data might also be more accessible, as visual novel promotional websites tent to feature character information of a different nature. Within VNDB we have a total of 9943 female characters with a listed blood type, out of a total of 68460 female character entries (as of July 12th 2021) 16% of all female characters. At the same time we have a total 4899 male characters with a listed blood type, out of a total of 33506 male character entries, 17.12% of all male characters.

ACDB, on the other hand allows us to see a more comprehensive view of the field of Japanese visual media, but it suffers from a high variance in the available data. Its free-form tag system, for example, results in a large number of very disparate tags which are not evenly distributed across the dataset. One example is ‘Large Eyebrows’, which tags 173 characters out of 112114 total entries (as of July 12th 2021), circa 0,15% of the total population of characters. Regarding character blood type, ACDB has a total of 4725 characters out of 107369 entries with a listed blood type, about 4.40% of all entries. Of these 4725, 2796 are female (4.48% of 62307 character entries) and 1906 are male (4.53% of 42073 character entries), while 18 are labeled as “Not Applicable” (0.72% of 2497 character entries) and 5 more are labeled as “Unknown / Ambiguous” (1,17% of 426 character entries). No character entry whose gender is listed as “many” or “Androgynous” has a listed blood type.

Our two datasets seem to suggest that blood type is either more important in visual novel game design or that the community around VNDB deems it more relevant to record. This is in contrast with the preconception that might arise by looking at highly popular media franchises such as Attack on Titan. Listing a character’s blood type might not be as wide-spread as its usage in highly popular works might suggest. Another possibility is that such information might not be easily accessible to users compiling the data: information such as character blood type is usually not given within the media-proper but through peripheral texts such as data books or interviews, which might not be completely available due to language barriers, among other factors. On the other hand, promotional sites for visual novel games often include character information that is more accessible to general users in the form of key visual features, blood type and a brief text summarizing the character’s backstory.

Building on these results, the next step is to try and see if the actual blood type personality theory can be mapped onto existing character personalities, in the characters which have a listed blood type. While it is not possible to attempt this with the ACDB data, it is possible within our VNDB dataset. We will discuss this exploration in the second part of this blogpost.


  • Kanazawa, M. 2021. Relationship between ABO Blood Type and Personality in a Large-scale Survey in Japan. International Journal of Psychology and Behavioral Sciences.
  • Yamazaki K, Sakamoto A. Self-fulfillment phenomenon generated by blood-typical personality stereotypes: time-series analysis of nation-wide survey. 32nd Annual conference of Japanese society of social psychology. 1991; 32: 289-292.
  • Sato T, Miyazaki S, Watanabe Y. 1991. An examination of the blood type personality relationship theory (3) from stereotype to prejudice. 2nd convention of Japan Society of Development Psychology 147.
  • Watanabe Y. 1994. The roles of prototype and exemplar in the formation of the “blood type stereotype”. Japanese Statistical study on personality differences by blood type. Japanese Journal of Social Psychology 10(2): 77-86.

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