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I'm such an optimist that my doctor told me my blood type was B Positive.
Mark Rosewater, Magic: The Gathering R&D

In much of Asia, especially well-known in Japan, blood types are seen to determine personalities. Wikipedia summarizes this theory as follows:

  • Type A
    • Best Traits: Earnest, sensible, reserved, patient, responsible, and cautious.
    • Worst Traits: Fastidious, overearnest, stubborn, tense, obsessive and pessimistic.
  • Type B
    • Best Traits: Passionate, active, creative, animal-loving, flexible, cheerful, optimistic.
    • Worst Traits: Irresponsible, forgetful, selfish, lazy, impatient, unreliable, and "going own way."
  • Type AB
    • Best Traits: Cool, controlled, rational, sociable, adaptable, intelligent.
    • Worst Traits: Critical, indecisive, unforgiving, two-faced, aloof and "split personality."
  • Type O
    • Best Traits: Confident, self-determined, ambitious, strong-willed, intuitive, agreeable, competitive and athletic.
    • Worst Traits: Self-centered, cold, aggressive, unpredictable, arrogant, envious and ruthless.

It's common in any series where it's All There in the Manual to list the blood type of all the characters. Incidentally, the practice started as a type of pseudo-scientific propaganda: One group of people rebelled against invasion while another simply accepted the invaders. Since the two groups had different blood-types, the army doctors simply claimed that it was their blood-types making them rebel, rather than accept that just maybe, most people don't like having their country invaded. Interestingly, there used to be machines in public places which would tell your blood type, but they were removed after the health issue associated with shared needles became more apparent.

It's said that the predominant blood type in Japan is A, with about 40% of the population, while Americans tend toward O, about 37%. It's also estimated that more than 99% of the Japanese are Rh+, so the familiar +/- seen after American blood types can usually be dispensed with.

The Theory was also the basis for a Japanese eugenics program during WW 2, and has since been disproven.

Compare Four-Temperament Ensemble (or five), wherein the temperaments line up best:

Type A Type AB Type B Type O
Melancholic or Supine Phlegmatic Sanguine Choleric

See also AB Negative and The Power of Blood.

Examples of Personality Blood Types include:

Anime and Manga

  • Blue Exorcist includes the info for some For those wondering, Rin is type A, Yukio and Shura are both type O, Shiemi and Bon are both type B. Fujimoto's a type AB and Mephisto's isn't given.
  • The manga of Cardcaptor Sakura gives blood types for most (if not all) characters. Even the nonhuman ones.
  • In The Cherry Project Chieri calls Love Interest Tsuzuki a "Typical A" and he calls her a "Typical B" back.
  • Cowboy Bebop's four heroes have each a different blood type: Jet (A), Ed (AB), Faye (B), and Spike (O).
  • Kamiyama, Hayashida and Maeda deduce that the enigmatic Freddie of Cromartie High School is a B-type from looking at his completely unpredictable movements (sumo teppo practice shows him to be an A type and holding a textbook upside down is considered either a B type or an AB type).
  • D.Gray-man includes this information (along with birthdates and nationalities) for all major characters up to about volume 18. Most of them are All There in the Manual in the fanbook, though.
  • How to Read, the final volume of Death Note, gives the blood type of all the major players (save L) and several minor characters. Light, Mello, Mikami, Soichiro, Naomi Misora, and Demegawa had A. Near, Matsuda, and Watari had B. Misa, Takada, and Kyosuke Higuchi had AB. Raye Penbar, Matt, and the female members of the Yagami family had O.
  • The issue pops up in a chapter of Franken Fran, in which the school becomes obsessed with the theory to the point that it causes social splits and discrimination. This causes problems for Adorea, whose dominant blood type is constantly changing due to the sheer number of organs she stores in her body.
  • Volume 6 of the Harukanaru Toki no Naka de manga includes a scene with Akane, Tenma and Shimon trying to guess the blood types of the Hachiyou based on their personalities.
  • In Volume 4 of Ichigo Mashimaro, there's a Q&A with a couple of questions breaking up the chapters. Blood type is asked early on. To compare:
    • The Ito sisters, Chika and Nobue, share blood type A.
    • Miu is type B.
    • Ana is type AB.
    • Matsuri is type O.
  • Pretty much the entire point of Ketsuekigata-kun!, which centers around personifications of the four ABO blood types. Each of the four types is voiced by an actor who has that blood type.
  • Subversion and possibly, a deconstruction: In episode 9 of Lucky Star it turned out that the personality types according to blood type were almost completely inaccurate. For the record, the characters examined were Kagami and Tsukasa Hiiragi, which logically speaking, have both the same blood type because they are twins, yet they have distinctly different personalities.
  • Lampshaded in Magic Knight Rayearth, Fuu includes her blood type when introducing herself to Hikaru and Umi. Mystified, they ask why; and she hastily replies in case she needs medical attention.
  • Mahou Sensei Negima: 28 of 31 class members have a blood type listed (they get a small bio page in their introduction chapter in the manga) and they all fit very well. Now has its own page here.
    • Negi is type AB which very much fits his personalty also fits his parents personalities his father would be a Type B and his Mother fits Type A very well.
      • It also befits his status as the center of the harem. AB is compatible with everyone.
  • Parodied in Medaka Box, where every character has type AB.
  • A recent Naruto Shippuden episode deals with this. Orochimaru asks whether Kabuto is a Type A, much to his chagrin that he's AB.
    • Two characters that share blood-types Naruto and the Fourth Hokage, aka Namikaze Minato were eventually revealed to be related. Not that surprising though...
      • As a matter of fact, Naruto's mother Uzumaki Kushina is the same blood type as well.
    • In the databooks, each character's blood type is listed. Interestingly, the medic of Naruto's team (Sakura) has O-type blood. This makes her a universal donor.
      • Also, Hinata is an A-type. This is funny because both O-types and A-types are incompatible with B-types (Naruto is a B-type). B-types are compatible with AB-types. Guess which of Naruto's teammates is an AB-type?
      • Karin also happens to be AB type, and since she has also met Naruto and is now on Konoha, well...
  • And there's a One Piece entry. In an SBS Oda revealed the Straw Hats' blood types this way:
    • Nami, Chopper & Brook (X), Zoro & Franky (XF), Usopp & Robin (S), Sanji (S, Rh-), and Vivi, Luffy & by extension, Jinbe (F).
    • The catch is that Oda explained that the nomenclature isn't uniform yet, so there are people out there that use "A, B, O/C, AB" pattern. So if A -> X, B -> F, and S -> O, we get the trope played straight (with the curious exceptions of Usopp, Franky, and Brook.
  • Ouran High School Host Club has an absolutely hilarious scene where the Creepy Twins convince the lead girl that the resident moe boy is actually evil to the core by pointing out that he has the same blood type (AB) as The Chessmaster of the club. The main character immediately broke the Fourth Wall to apologize to any viewers with AB blood type.
  • In Revolutionary Girl Utena, one episode has a tidbit where Nanami and her posse discuss the blood type-personality correlation. It reveals that, while their parents and Nanami have Type B blood, Touga (her Aloof Big Brother) has Type A, which should be impossible... it turns out that both of them were adopted. Although, due to how shaky things were getting between the two and the fact that she had been too young to remember, Nanami automatically assumes that just Touga was adopted...
    • There's also this scene:

 Utena: Himemiya, you're type-AB, right? Let's see, type-ABs are elusive and seldom reveal their true feelings, huh?

Anthy: And you're type-B, right, Utena-sama? Type-Bs are self-centered and prone to misconceptions...

Utena: Yeah, sorry, okay.

  • The cast of Ronin Warriors follow the bloodtypes to the T
    • Ryo Sanada and Shuu Rei Fuan are Type O
    • Seiji Date is A
    • Shin Mouri is B
    • Touma Hashiba is AB
  • In Sailor Moon, all of the main characters and a few of the minor ones have their blood types listed.
    • Type O: Usagi/Sailor Moon, Chibiusa/Sailor Chibi Moon, Makoto/Sailor Jupiter, Michiru/Sailor Neptune, Haruna/sensei
    • Type A: Mamoru/Tuxedo Mask, Ami/Sailor Mercury, Setsuna/Sailor Pluto, Seiya/Sailor Star Fighter
    • Type AB: Rei/Sailor Mars, Hotaru/Sailor Saturn, Taiki/Sailor Star Maker, Naru
    • Type B: Minako/Sailor Venus, Haruka/Sailor Uranus, Yaten/Sailor Star Healer
  • In Sketchbook many characters' personalities seem to fit their stated blood types. Hazuki Torikai (type A) is the straightest example, which is lampshaded several times in the manga. However, Sora Kajiwara (Type A) and Daichi Negishi (Type AB) are subversions, which is also lampshaded.


  • In Volume 4 of Strawberry Marshmallow, there's a Q&A with a couple of questions breaking up the chapters. Blood type is asked early on. To compare:
    • Type A: the Ito Sisters Chika & Nobue
    • Type AB: Ana
    • Type B: Miu
    • Type O: Matsuri
  • In Weiss Kreuz, the personalities of the four original members of Weiss are all fairly well-matched to their respective blood types : Omi is type O, Aya is type A, Ken is type B, and Youji is type AB.
  • You could say that this is subverted in Yu-Gi-Oh with main character Yugi Moto possessing type AB Negative blood. Cool, controlled and unforgiving definitely aren't the best choice of words to describe him.
    • They are, however, a good choice of words to describe his alter-ego Yami Yugi, who shares his blood type on account of sharing his body.
    • Also, a sub-characteristic associated with AB blood type is Split Personality. Or an least mood swings. Which Yugi has. In spades.
    • It's played straight with Bakura, who is also type AB.


  • Averted in South Korean girl group's nu song NU ABO, where it describes a completely different personality symbolized by a nonexistent blood type called ABO.

Live Action TV

  • House is type AB ("Universal Reciever"); Wilson is type O ("Universal Donor").

Video Games

  • Generally, shows up in promotional material for any JRPG. If this gets included in Western promotional material due to poor editorial oversight, expect some head-scratching, since in the West blood types don't have any significance attached to them.
  • As a Western game with Japanese influences, Battle-Girl lists its heroine's blood type among her vital stats. It's B, which suits her.
  • The Indie RPG Cthulhu Saves the World has Umi, one of the party members, bring this up as banter. Umi states that her blood type is B+, making her a cheery person. This is averted by the fact that the other party members are an Outer-God-turned-hero, a talking sword, a necromancer, an alien, a crazy priest and a demon dragon. These members respectively have ink, nothing, a lengthy soliloquy of pain, Uranium, and acid. The old man is insane and therefore cannot remember his blood type.
  • Crazy Taxi, at least in the manual.
  • Each character in Death Smiles has their blood type listed in the manual.
  • Dungeon Keeper creatures had blood types listed, for no apparent reason. It also lampshades itself with the scrolling help text if you point at a creature's blood type listing: "As if you care. Blood is blood, right?"
  • Shockingly, Cloud Strife from Final Fantasy VII fits the AB blood type 'personality' almost to a T. Guess which blood type he is.
  • The Japanese version of Fire Emblem 7 allows the player to chose Mark's (the tacticians) blood type; this is removed in every other version (Along with Birth Month, the exclusive factor outside of Japan, it decided your affinity. Hence why twins can have separate affinity in 6/7.).
  • In Mana Khemia, the fact one character lacks a blood type in the manual foreshadows the game's Tomato in the Mirror reveal.
  • In the Princess Maker games, stats are determined by blood type. And in 2, it also determines how stressed the girl gets.
  • The original Resident Evil had an intro with profiles of all the characters, including blood types.
    • And all the other characters introduced later get blood types too. Interestingly enough, all the villains seem to have type O.
  • Another Japanese-influenced game, Skullgirls, also has blood types for each of the characters, and they correspond pretty well. Some of the characters, however, don't have standard blood types — among them SG (for Skullgirl), enbalmed (for Squigly), and B# (for Big Band).
  • Soul Calibur took this to a new level of absurdity: all the characters had ABO/Rh blood types in their profile. The game is set in 1587. ABO was not discovered until 1901.
    • Proof that Soul Calibur was an Anachronism Stew even before the inclusion of Jedi and Lightsabers.
    • In general, most fighting games include blood type in character biographies. Needless to say, it's probably need to know information for Mortal Kombat.
    • Amusingly enough, Edgemaster (who randomly uses a non boss characters moveset) has a blood type of O.
    • And Ivy's blood type is "Soul Edge."
  • An early PA in Star Ocean Till the End of Time gives the player the option of choosing Fayt's blood type. Each choice either raises or lowers the affection of certain party members, giving insight into what personality types they like and which ones they don't.
    • Judging from Fayt's actual personality in the game, Type O seems to be his blood type by default (since the two that go up from this are Sophia (his childhood friend) and Albel.) To support the fact that he remains optimist throughout the game, agrees to almost everything and is very sociable to the point where he makes friends easily. Also, if the group were to ever get ambushed, he announces that "He was careless!"
  • When Street Fighter II came out, character biographies included blood type.
  • The Super Robot Wars series often lets the player select the birthday and blood type of the Original Generation main protagonist. While at first appearing purely cosmetic, their command lists are directly derived from the selection, divided by what astrological sign the birthday falls under and the blood type for a total of forty-eight possibilities. Selecting 11/11 B, the birthday and blood type of head producer Takanobu Terada, provides an Easter Egg set of commands that are usually the ideal possible set or close to it, while the character's default birthday and blood type provide another unique set that normally matches what the character will use should s/he appear in any other games in the franchise.
  • In Valkyrie no Bouken, you get to choose a blood type at the beginning. Whereas blood type doesn't establish your personality type, it does affect the rate at which you level up: A --> normal, B --> precocious, O --> late-blooming, and AB --> random.
  • In the Hentai RPG Maker game Violated Heroine, you can customize the heroine's blood type at the beginning of the game to raise combat stats: Type A grants more Agility but less Spirit, Type B more Attack but less Defense, Type O more Defense but less Attack, and Type AB more Spirit but less Attack.


  • In Blip, after the Friendly Neighborhood Vampire consumes several gallons of Type B blood, she suddenly shows an impulsive streak, and the author speculates in The Rant that this trope is in play.
  • Parodied in Evil Inc.
  • In the Narbonic Director's Cut, Shaenon Garrity mentions that she had blood types worked out for the Narbonic characters. (Mell is revealed to be Type B.) The cast page for Skin Horse includes blood types, including for the nonhuman characters.
    • As far as regular human blood types go, Tip the really-getting-around psychologist as Type O, Dr. Lee the Only Sane Woman as Type AB, and Tigerlily Jones the insanely creative Seventies-themed Mad Scientist as Type B.
    • Which was then subverted when it was revealed that she's who Unity's blood technically is.