Aboworld
Brother Lu is not a defective product, he was assigned to Class D just because of O's gender.
The number of o is a little less than A, just a little
There are also a certain number of o and A in the school, but the quantitative relationship is: B>A>O
The ABO relationship in this world is relatively equal, but in some specific abilities A>O>B
Attention! Brother Lu is still very strong, and because he is in the white room, Brother Lu, the O, is not very sensitive to A's pheromones, but he still feels a bit lost.
Intention: Brother Lu NB