Tbh, I rarely root for either of the love interests in a love triangle. Authors just can't seem to give MCs two equally great people to fall in love with lol.
The prosecutor is a selfish, self-serving asshat who's only looking out for his career but IMO, boss is looking worse. The beginning suggests that boss is actually secretly pining for MC so why tha duck did he let MC get into this situation. He couldn't give MC a loan so he wasn't so insecure about his finances and felt his only option was to be a drug mule? It's giving Taeju 2.0. I mean, maybe he'll prove me wrong since he's probably the sperm donator and endgame but I don't have a lot of faith in BL writing lol.
Also, I don't think MC would have slept with the prosecutor if the boss hadn't primed him to view his body as currency for survival.
I love how the prison mate talks to his baby lol