Did you actually read the story? the Omega is the one who left and tried to hide the child.
You must have read the wrong story....the alpha was in rut and the omega must have manifest right before the rut and also went into heat. That's why the omega got pregnant, because their cycle aligned. The beat didn't know he manifested, most likely, or if he knew he didn't think he'd go into heat. Either way he happened have been there during DoYoon's rut, and then he ran away right after the sex. DoYoon had NO RECOLLECTION of the event except that he found out he had been bonded to some omega...and after DY broke up w/ YeJun, YeJun just left after graduation and ran away and found out he was pregnant and decided to go into hiding and raised the child alone. In NO WAY did DoYoon neglected his child...and mate because he did not know... Idk why it took him 5 years to find YJ though. YJ must have hid pretty well, and maybe DY hadn't gone to look for YJ because he hadn't associated the two and two together. Most likely YJ did a good job of hiding. That's my guess.
SORRY READING COMPREHENSION GOT ME :SOB:
bro rawdogged him and left him with a child to take care of then comes back after 5 tears like “Yo I’m back with the milk” like wtf??? Also I don’t like how the story is just… so bland, like it was written by a female wattpad writer trying to write a omegaverse story for the first time