
Though I don't like either of them, I've just gone through a sea of white-haired ML enthusiasm. One thing I think people are forgetting is that after being admitted to the hospital, prosecutor's medical connection stated likely nothing bad happened internally because MC has a high tolerance for the drug already. Since it was supposed to help with fertility?(maybe not with omegas) and MC is so uncertain about if he wants the baby or not, this means someone has been dosing him.
The suspects are: drug dealer, prosecutor, his mom taking a trial drug (since this drug was released seven years after he was born) while pregnant with him so he was born with it, or one of his now parents (we don't know much about his dad at all and though his stepmom seems to care, it's a trope that leaves in in the line up.) I kinda feel it's in the order of likelihood.
By far, the drug deal is the strongest because not only does he have access and we see that he bought back some product he smuggled in, we open up to him having wanted sex with MC for a while and being rejected. The prosecutor knows what it is and seems a bit shady but he's romantically nonchalant and seems like he's more into responsibility topped with slight rebellion against his father. We know his birth mom left when he was young and things were rough. MC doesn't feel like he knows what family is and doesn't have the confidence that he can follow through with this child. The closest person in his family currently is his brother, which would be a weird angle and poor "twist villain" in this situation so I left him off the line up.
I hope the prosecutor is the father. Seems like the more stable choice for raising a family honestly. But its probably gonna be the white haired bc these BL always pick the worst option.