This is actually a great concept for talking about STDs. The MC now has a responsibility to make sure his bodily fluids aren't ingested by another. He has to find a community of people who also suffer with his condition, to figure out why it happened and how to deal with this. He now has limited options in who he can intimately interact with, which may lead to him grasping at the only straw he has, which is the sick fuck who purposefully infected him.
The ML is the exact example of what not to do. No one in universe has made excuses for him. Everyone has acknowledged that he is fucked up and wrong, including himself. He doesn't feel bad about what he has done, because he wants the MC, and he didn't care about anything else. His backstory is tragic, because there are teens this happens to. There are teens who have STDs and don't know until it is too late for another person. Which makes his actions now that much worse. He targeted another person who loves food (MC actually loving food so much he has it as his phone background is adorable), because he knew that he could force that person to rely on him. He then took the opportunity to rape MC. ML is awful, and I don't think we are supposed to like him.
What I would like to see this series do, is break the, the first two dudes we see are the seme and uke trope. MC may have to deal with ML for a while, but I actually hope he finds someone else who can help him. I don't even mind if it is platonic, if it is straight (because we don't even know MCs sexuality), or if it comes in the form of a Dr or scientist. The ML, should not be the ML.
I don't actually want to have a series where we toss aside the ML either. I would like to see him have to suffer the consequences of his actions. He raped MC. He should be in jail. Like, I want him to go to jail. Intentionally giving people an STD is also jail worthy. Accidentally, I can accept, because you can't inform someone about something you don't know yourself.
Honestly, I have a bit of hope for this series. The fact that we already have 2 characters who are dating, with one being infected and the other not, shows that people can be in relationships even with STDs. My mom is actually one such person. Because she takes responsibility, making sure to never have sex with my stepfather during an outbreak (she is only infectious when she has symptoms) he has not gotten infected. They've been married 15 years.
I love this concept, I hope MC gets a non rapist person in his life to help him. ML can fuck off and go to jail.