Here in the West, it's been quite a mystery why Japanese anime and manga profiles invariably list the blood type for characters and actors alike.
Half of us over in Europe couldn't tell you our own blood group, let know know why we need to know yours.
Today is Light Yagami's 30th birthday. To mark the date, we embarked on a mission to find out why Kira's blood was so important to his destiny. Other than the fact it was killing him at the end there; you know, leaking in great puddles on the floor like that.
It seems that to the Japanese, blood groups are all about destiny, insofar as such things are driven by the personality.
Asian Blood Type Personae: What They Do in Lieu of Star-Signs in the East
Each blood type is associated with a list of character attributes; in much the same way as those in the West might ask for a star-sign, in order to quickly gain insight into a new associate's general complexion.
Here traits of psyche, in all their virtues and flaws, are said to be clustered around certain dates of birth here; grouped into categories headed by the twelve signs of the zodiac; then randomly applied to all born under their auspices.
Virgos are tidy to the point of OCD; Scorpios will stab you in the dark; Cancerians are delicate, little flowers to be nurtured lest they cry; Librans are indecisive; Sagittarians are sporty; Leos are Kings and Queens of their lives, and yours; and Aquarians are dawning a New Age, where we'll all run around with flowers in our hair, letting the sunshine in.
You know the sort of thing, stereotypes all. Nevertheless a kind of cultural short-hand for how anyone might act in any given situation; widely believed and relied upon, even against any data to the contrary, with no more empirical evidence than knowing a person's birthday.
Probably sounds a little mad to someone watching from Japan.
Just as Western tabloids and TV magazine programmes run horoscopes - describing the immediate future, as deemed accurate for all born between two month-straddling dates x 12 - their Japanese counterparts do the same for blood types.
Knowing the scientific classification of the contents of your veins is not only useful for blood transfusions. It can also predict the shape of your day, not to mention being forewarned regarding your compatibility with potential love partners.
A Blood Type Personality in Death Note's Light Yagami
So where does Kira fit into all this? Very well actually.
But then it's quite a thing for mangaka to link their characters with blood group types, and to ensure that their personalities fit that classification precisely. So widespread, there's a TV Trope entry calling them out on it. So Kira really should match his type here.
Tsugumi Ohba reveals, in Death Note 13: How to Read, that Kira's blood type was A. It could probably have been guessed anyway. Apparently the A blood group is the most prevalent in Japan. Hence Light Yagami's personality should be pretty common amongst the Japanese. Quite worrying that.
However, no list of attributes associated with blood type A people has so far mentioned 'global slaughter on a massive scale' nor yet 'become God'. It may mean that Kira is atypical amidst his inherited antigenic kin.
Instead Light Yagami's A blood type personality should be:
I can't help feeling a little sorry for Ms Spears there. Or nervous. I dunno.