I was watching Kimetsu no Yaiba season one when it happened.
Remember when this guy, Kiyoshi, who was captured by a demon because of his special blood type, appeared?
Well, when I saw this "Marechi" thing again, I remembered how in the Shadowhunters TV on numerous occasions we see Simon (or other vampires) specifically asking for O- blood, and I also remembered how in My Babysitter is a Vampire the Vampire nurses want Ethan's blood because he is Rh negative, in their own words, "one in a million."
It should be noted that I'm not an expert in blood and I don't study anything related to the health sector, so I only have basic knowledge.
Why would vampires like blood type O–? Dude, blood is made up of proteins, antigens, and stuff.
Why would blood that does not have any of these proteins and antigens be the favorite? I imagine that for vampires, it must be the equivalent of water.
Maybe it's just me, but I imagine a blood type that contains more stuff must taste better.
Now, my sister suggested that maybe they like it more because of the rarity, so I took my time to investigate if O– was the less common blood type, and it turned out not to be.
The least common blood type is AB–. Why then? Maybe Ethan was type AB– since they don't say anything specific (if I remember correctly) but I certainly remember other vampires who loved blood type O–.
So why?
