beta
Theory 1 : Byul is dominant omega. Do you remember Dojin's family are all alphas except his mom and they treated omega very preciously? If Byul is omega, he would be the first omega grandson from the rich fam. They would spoiling him rotten.
Theory 2 : Byul is alpha. Could be alpha x alpha. Or alpha x beta. Or... The it could be masculine omega X feminine alpha (byul).
Ps: now Byul is grown up. I need few more years for my baby boo Yiho to see his love life. We are grandmas now..lmao