Mm so the different stars groups represent the blood types? Not bad

I was just thinking the same thing. That could be the only reason that the peoples status does not mean anything !

I wonder what Ciel's would be since they consider it so rare. AB? But I wonder if it's plus or negative.

While they do have the blood groups do they know about RH? How pluses can't go into negatives but negatives can go into pluses? Which is why O- is the universal donator?

I'm also curious if the affects of the demon deal will reflect in his blood?