.
Wait after ch 19
Ch 11-13ish is when the alpha explained to omega main about his mom and her situation. The mom expanded her story of her happiness with a beta was quickly extinguished when she meets an alpha and she feels guilt after she realized she couldn't have a child with the alpha so everyone ostracized her. She fears her beta ex husband and her only child would resent her. So she blames herself for not picking an alpha in the first place to avoid all this mishap and hurting ppl. Main reassured her without her with beta, she wouldn't have gotten a son who was bow succeeding. But after her story, main doesnt want to experience what she did and decided to cut ties with his beta bf to avoid hurting him in case he meets an alpha and ends up leaving him.
Erito Ω Wa Yoru ni Oborete