PolarBear's manga / #Unknown gender(1)

Ch 1 Omegaverse Keisei Amamiya x Itsuki Amamiya's only contain alphas... but keisei's as an omega was a mistake which led him to hate omegas... becoz he was shunned by all surrounding him. So he locks himself up. When itsuki joined, he was considered an unknown gender which was suitable to stay beside kesei sama. When Ujou (older bro) told him to serve kesei .. and itsuki saw his servant and him having sex... he felt something weird about his body. In the morning when he went to the bathroom to wash off his pants, kesei was present there and felt his pheromones! ??